diff --git a/packages/smooth_app/lib/pages/product/category_cache.dart b/packages/smooth_app/lib/pages/product/category_cache.dart
new file mode 100644
index 00000000000..50789a82c96
--- /dev/null
+++ b/packages/smooth_app/lib/pages/product/category_cache.dart
@@ -0,0 +1,117 @@
+import 'package:openfoodfacts/openfoodfacts.dart';
+
+/// Cache where we download and store category data.
+class CategoryCache {
+  CategoryCache(this.language);
+
+  /// Current app language.
+  final OpenFoodFactsLanguage language;
+
+  /// Languages for category translations.
+  List<OpenFoodFactsLanguage> get _languages => <OpenFoodFactsLanguage>[
+        language,
+        _alternateLanguage,
+      ];
+
+  /// Where we keep everything we've already downloaded.
+  final Map<String, TaxonomyCategory> _cache = <String, TaxonomyCategory>{};
+
+  /// Where we keep the tags we've tried to download but found nothing.
+  ///
+  /// e.g. 'ru:хлеб-украинский-новый', child of 'en:breads'
+  final Set<String> _unknown = <String>{};
+
+  /// Alternate language, where it's relatively safe to find translations.
+  static const OpenFoodFactsLanguage _alternateLanguage =
+      OpenFoodFactsLanguage.ENGLISH;
+
+  /// Fields we retrieve.
+  static const List<TaxonomyCategoryField> _fields = <TaxonomyCategoryField>[
+    TaxonomyCategoryField.NAME,
+    TaxonomyCategoryField.CHILDREN,
+    TaxonomyCategoryField.PARENTS,
+  ];
+
+  /// Returns the siblings AND the father (for tree climbing reasons).
+  Future<Map<String, TaxonomyCategory>?> getCategorySiblingsAndFather({
+    required final String fatherTag,
+  }) async {
+    final Map<String, TaxonomyCategory> fatherData =
+        await _getCategories(<String>[fatherTag]);
+    if (fatherData.isEmpty) {
+      return null;
+    }
+    final List<String>? siblingTags = fatherData[fatherTag]?.children;
+    if (siblingTags == null || siblingTags.isEmpty) {
+      return fatherData;
+    }
+    final Map<String, TaxonomyCategory> result =
+        await _getCategories(siblingTags);
+    if (result.isNotEmpty) {
+      result[fatherTag] = fatherData[fatherTag]!;
+    }
+    return result;
+  }
+
+  /// Returns the best translation of the category name.
+  String? getBestCategoryName(final TaxonomyCategory category) {
+    String? result;
+    if (category.name != null) {
+      result ??= category.name![language];
+      result ??= category.name![_alternateLanguage];
+    }
+    return result;
+  }
+
+  /// Returns categories, locally cached is possible, or from BE.
+  Future<Map<String, TaxonomyCategory>> _getCategories(
+    final List<String> tags,
+  ) async {
+    final List<String> alreadyTags = <String>[];
+    final List<String> neededTags = <String>[];
+    for (final String tag in tags) {
+      if (_unknown.contains(tag)) {
+        continue;
+      }
+      if (_cache.containsKey(tag)) {
+        alreadyTags.add(tag);
+      } else {
+        neededTags.add(tag);
+      }
+    }
+    final Map<String, TaxonomyCategory>? partialResult;
+    if (neededTags.isEmpty) {
+      partialResult = null;
+    } else {
+      partialResult = await _downloadCategories(neededTags);
+    }
+    final Map<String, TaxonomyCategory> result = <String, TaxonomyCategory>{};
+    if (partialResult != null) {
+      _cache.addAll(partialResult);
+      result.addAll(partialResult);
+      for (final String tag in neededTags) {
+        if (!partialResult.containsKey(tag)) {
+          _unknown.add(tag);
+        }
+      }
+    }
+    for (final String tag in alreadyTags) {
+      result[tag] = _cache[tag]!;
+    }
+    return result;
+  }
+
+  // TODO(monsieurtanuki): add loading dialog
+
+  /// Downloads categories from the BE.
+  Future<Map<String, TaxonomyCategory>?> _downloadCategories(
+    final List<String> tags,
+  ) async =>
+      OpenFoodAPIClient.getTaxonomyCategories(
+        TaxonomyCategoryQueryConfiguration(
+          tags: tags,
+          fields: _fields,
+          languages: _languages,
+        ),
+      );
+}
diff --git a/packages/smooth_app/lib/pages/product/category_picker_page.dart b/packages/smooth_app/lib/pages/product/category_picker_page.dart
new file mode 100644
index 00000000000..cc7c5118191
--- /dev/null
+++ b/packages/smooth_app/lib/pages/product/category_picker_page.dart
@@ -0,0 +1,168 @@
+import 'package:flutter/cupertino.dart';
+import 'package:flutter/material.dart';
+import 'package:openfoodfacts/openfoodfacts.dart';
+import 'package:provider/provider.dart';
+import 'package:smooth_app/database/local_database.dart';
+import 'package:smooth_app/pages/product/category_cache.dart';
+import 'package:smooth_app/pages/product/common/product_refresher.dart';
+
+/// Category picker page.
+class CategoryPickerPage extends StatefulWidget {
+  CategoryPickerPage({
+    required this.barcode,
+    required this.initialMap,
+    required this.initialTree,
+    required this.categoryCache,
+  }) {
+    initialTag = initialTree[initialTree.length - 1];
+    initialFatherTag = initialTree[initialTree.length - 2];
+    // TODO(monsieurtanuki): manage roots (that have no father)
+  }
+
+  final String barcode;
+  final Map<String, TaxonomyCategory> initialMap;
+  final List<String> initialTree;
+  final CategoryCache categoryCache;
+  late final String initialFatherTag;
+  late final String initialTag;
+
+  @override
+  State<CategoryPickerPage> createState() => _CategoryPickerPageState();
+}
+
+class _CategoryPickerPageState extends State<CategoryPickerPage> {
+  final Map<String, TaxonomyCategory> _map = <String, TaxonomyCategory>{};
+  final List<String> _tags = <String>[];
+  String? _fatherTag;
+  TaxonomyCategory? _fatherCategory;
+
+  @override
+  void initState() {
+    super.initState();
+    _refresh(widget.initialMap, widget.initialFatherTag);
+  }
+
+  @override
+  Widget build(BuildContext context) {
+    final LocalDatabase localDatabase = context.read<LocalDatabase>();
+    return Scaffold(
+      appBar: AppBar(
+          title: const Text('categories')), // TODO(monsieurtanuki): localize
+      body: ListView.builder(
+        itemBuilder: (final BuildContext context, final int index) {
+          final String tag = _tags[index];
+          final TaxonomyCategory category = _map[tag]!;
+          final bool isInTree = widget.initialTree.contains(tag);
+          final bool selected = widget.initialTree.last == tag;
+          final bool isFather = tag == _fatherTag;
+          final bool hasFather = _fatherCategory!.parents?.isNotEmpty == true;
+          final Future<void> Function()? mainAction;
+          if (isFather) {
+            mainAction = () async => _displaySiblingsAndFather(fatherTag: tag);
+          } else {
+            mainAction = () async => _select(tag, localDatabase);
+          }
+          return ListTile(
+            onTap: mainAction,
+            selected: isInTree,
+            title: Text(
+              widget.categoryCache.getBestCategoryName(category) ?? tag,
+            ),
+            trailing: isFather
+                ? null
+                : category.children == null
+                    ? null
+                    : IconButton(
+                        icon: const Icon(CupertinoIcons.arrow_down_right),
+                        onPressed: () async => _displaySiblingsAndFather(
+                          fatherTag: tag,
+                        ),
+                      ),
+            leading: isFather
+                ? !hasFather
+                    ? null
+                    : IconButton(
+                        icon: const Icon(CupertinoIcons.arrow_up_left),
+                        onPressed: () async {
+                          final String fatherTag =
+                              _fatherCategory!.parents!.last;
+                          final Map<String, TaxonomyCategory>? map =
+                              await widget.categoryCache
+                                  .getCategorySiblingsAndFather(
+                            fatherTag: fatherTag,
+                          );
+                          if (map == null) {
+                            // TODO(monsieurtanuki): what shall we do?
+                            return;
+                          }
+                          setState(() => _refresh(map, fatherTag));
+                        },
+                      )
+                : selected
+                    ? IconButton(
+                        icon: const Icon(Icons.radio_button_checked),
+                        onPressed: () {},
+                      )
+                    : IconButton(
+                        icon: const Icon(Icons.radio_button_off),
+                        onPressed: mainAction,
+                      ),
+          );
+        },
+        itemCount: _tags.length,
+      ),
+    );
+  }
+
+  void _refresh(final Map<String, TaxonomyCategory> map, final String father) {
+    final List<String> tags = <String>[];
+    tags.addAll(map.keys);
+    // TODO(monsieurtanuki): sort by category name?
+    _fatherTag = father;
+    _fatherCategory = map[father];
+    tags.remove(father); // we don't need the father here.
+    tags.insert(0, father);
+    _tags.clear();
+    _tags.addAll(tags);
+    _map.clear();
+    _map.addAll(map);
+  }
+
+  /// Goes up one level
+  Future<void> _displaySiblingsAndFather({
+    required final String fatherTag,
+  }) async {
+    final Map<String, TaxonomyCategory>? map =
+        await widget.categoryCache.getCategorySiblingsAndFather(
+      fatherTag: fatherTag,
+    );
+    if (map == null) {
+      // TODO(monsieurtanuki): what shall we do?
+      return;
+    }
+    setState(() => _refresh(map, fatherTag));
+  }
+
+  Future<void> _select(
+    final String tag,
+    final LocalDatabase localDatabase,
+  ) async {
+    if (tag == widget.initialTag) {
+      Navigator.of(context).pop();
+      return;
+    }
+    final Product product = Product(barcode: widget.barcode);
+    product.categoriesTags = <String>[
+      tag
+    ]; // TODO(monsieurtanuki): is the last leaf good enough or should we go down to the roots?
+
+    final bool savedAndRefreshed = await ProductRefresher().saveAndRefresh(
+      context: context,
+      localDatabase: localDatabase,
+      product: product,
+    );
+    if (savedAndRefreshed) {
+      Navigator.of(context).pop(tag);
+    }
+  }
+}
diff --git a/packages/smooth_app/lib/pages/product/common/product_refresher.dart b/packages/smooth_app/lib/pages/product/common/product_refresher.dart
new file mode 100644
index 00000000000..e93afc687c6
--- /dev/null
+++ b/packages/smooth_app/lib/pages/product/common/product_refresher.dart
@@ -0,0 +1,77 @@
+import 'package:flutter/material.dart';
+import 'package:flutter_gen/gen_l10n/app_localizations.dart';
+import 'package:openfoodfacts/openfoodfacts.dart';
+import 'package:smooth_app/database/dao_product.dart';
+import 'package:smooth_app/database/local_database.dart';
+import 'package:smooth_app/database/product_query.dart';
+import 'package:smooth_app/generic_lib/buttons/smooth_action_button.dart';
+import 'package:smooth_app/generic_lib/dialogs/smooth_alert_dialog.dart';
+import 'package:smooth_app/widgets/loading_dialog.dart';
+
+/// Refreshes a product on the BE then on the local database.
+class ProductRefresher {
+  Future<bool> saveAndRefresh({
+    required final BuildContext context,
+    required final LocalDatabase localDatabase,
+    required final Product product,
+  }) async {
+    final AppLocalizations appLocalizations = AppLocalizations.of(context)!;
+    final bool? savedAndRefreshed = await LoadingDialog.run<bool>(
+      future: _saveAndRefresh(product, localDatabase),
+      context: context,
+      title: appLocalizations.nutrition_page_update_running,
+    );
+    if (savedAndRefreshed == null) {
+      // probably the end user stopped the dialog
+      return false;
+    }
+    if (!savedAndRefreshed) {
+      await LoadingDialog.error(context: context);
+      return false;
+    }
+    await showDialog<void>(
+      context: context,
+      builder: (BuildContext context) => SmoothAlertDialog(
+        body: Text(appLocalizations.nutrition_page_update_done),
+        actions: <SmoothActionButton>[
+          SmoothActionButton(
+            text: appLocalizations.okay,
+            onPressed: () => Navigator.of(context).pop(),
+          ),
+        ],
+      ),
+    );
+    return true;
+  }
+
+  /// Saves a product on the BE and refreshes the local database
+  Future<bool> _saveAndRefresh(
+    final Product inputProduct,
+    final LocalDatabase localDatabase,
+  ) async {
+    try {
+      final Status status = await OpenFoodAPIClient.saveProduct(
+        ProductQuery.getUser(),
+        inputProduct,
+      );
+      if (status.error != null) {
+        return false;
+      }
+      final ProductQueryConfiguration configuration = ProductQueryConfiguration(
+        inputProduct.barcode!,
+        fields: ProductQuery.fields,
+        language: ProductQuery.getLanguage(),
+        country: ProductQuery.getCountry(),
+      );
+      final ProductResult result =
+          await OpenFoodAPIClient.getProduct(configuration);
+      if (result.product != null) {
+        await DaoProduct(localDatabase).put(result.product!);
+        return true;
+      }
+    } catch (e) {
+      //
+    }
+    return false;
+  }
+}
diff --git a/packages/smooth_app/lib/pages/product/new_product_page.dart b/packages/smooth_app/lib/pages/product/new_product_page.dart
index a62519c546e..9833a9a0316 100644
--- a/packages/smooth_app/lib/pages/product/new_product_page.dart
+++ b/packages/smooth_app/lib/pages/product/new_product_page.dart
@@ -12,10 +12,13 @@ import 'package:smooth_app/data_models/user_preferences.dart';
 import 'package:smooth_app/database/dao_product_list.dart';
 import 'package:smooth_app/database/knowledge_panels_query.dart';
 import 'package:smooth_app/database/local_database.dart';
+import 'package:smooth_app/database/product_query.dart';
 import 'package:smooth_app/helpers/analytics_helper.dart';
 import 'package:smooth_app/helpers/launch_url_helper.dart';
 import 'package:smooth_app/helpers/product_cards_helper.dart';
 import 'package:smooth_app/helpers/ui_helpers.dart';
+import 'package:smooth_app/pages/product/category_cache.dart';
+import 'package:smooth_app/pages/product/category_picker_page.dart';
 import 'package:smooth_app/pages/product/common/product_dialog_helper.dart';
 import 'package:smooth_app/pages/product/knowledge_panel_product_cards.dart';
 import 'package:smooth_app/pages/product/summary_card.dart';
@@ -159,7 +162,44 @@ class _ProductPageState extends State<ProductPage> {
               UserPreferencesDevMode.userPreferencesFlagAdditionalButton) ??
           false)
         ElevatedButton(
-          onPressed: () {},
+          onPressed: () async {
+            if (_product.categoriesTags == null) {
+              // TODO(monsieurtanuki): that's another story: how to set an initial category?
+              return;
+            }
+            if (_product.categoriesTags!.length < 2) {
+              // TODO(monsieurtanuki): no father, we need to do something with roots
+              return;
+            }
+            final String currentTag =
+                _product.categoriesTags![_product.categoriesTags!.length - 1];
+            final String fatherTag =
+                _product.categoriesTags![_product.categoriesTags!.length - 2];
+            final CategoryCache categoryCache =
+                CategoryCache(ProductQuery.getLanguage()!);
+            final Map<String, TaxonomyCategory>? siblingsData =
+                await categoryCache.getCategorySiblingsAndFather(
+              fatherTag: fatherTag,
+            );
+            if (siblingsData == null) {
+              // TODO(monsieurtanuki): what shall we do?
+              return;
+            }
+            final String? newTag = await Navigator.push<String>(
+              context,
+              MaterialPageRoute<String>(
+                builder: (BuildContext context) => CategoryPickerPage(
+                  barcode: _product.barcode!,
+                  initialMap: siblingsData,
+                  initialTree: _product.categoriesTags!,
+                  categoryCache: categoryCache,
+                ),
+              ),
+            );
+            if (newTag != null && newTag != currentTag) {
+              setState(() {});
+            }
+          },
           child: const Text('Additional Button'),
         ),
     ]);
diff --git a/packages/smooth_app/lib/pages/product/nutrition_page_loaded.dart b/packages/smooth_app/lib/pages/product/nutrition_page_loaded.dart
index 0c9d483c9ed..fba0be8893a 100644
--- a/packages/smooth_app/lib/pages/product/nutrition_page_loaded.dart
+++ b/packages/smooth_app/lib/pages/product/nutrition_page_loaded.dart
@@ -7,14 +7,11 @@ import 'package:openfoodfacts/model/OrderedNutrients.dart';
 import 'package:openfoodfacts/openfoodfacts.dart';
 import 'package:openfoodfacts/utils/UnitHelper.dart';
 import 'package:provider/provider.dart';
-import 'package:smooth_app/database/dao_product.dart';
 import 'package:smooth_app/database/local_database.dart';
 import 'package:smooth_app/database/product_query.dart';
-import 'package:smooth_app/generic_lib/buttons/smooth_action_button.dart';
-import 'package:smooth_app/generic_lib/dialogs/smooth_alert_dialog.dart';
 import 'package:smooth_app/helpers/ui_helpers.dart';
+import 'package:smooth_app/pages/product/common/product_refresher.dart';
 import 'package:smooth_app/pages/product/nutrition_container.dart';
-import 'package:smooth_app/widgets/loading_dialog.dart';
 
 /// Actual nutrition page, with data already loaded.
 class NutritionPageLoaded extends StatefulWidget {
@@ -330,62 +327,15 @@ class _NutritionPageLoadedState extends State<NutritionPageLoaded> {
       _nutritionContainer.setControllerText(key, controller.text);
     }
     // minimal product: we only want to save the nutrients
-    final Product minimalProduct = _nutritionContainer.getProduct();
-    final bool? savedAndRefreshed = await LoadingDialog.run<bool>(
-      future: _saveAndRefresh(minimalProduct, localDatabase),
-      context: context,
-      title: AppLocalizations.of(context)!.nutrition_page_update_running,
-    );
-    if (savedAndRefreshed == null) {
-      // probably the end user stopped the dialog
-      return;
-    }
-    if (!savedAndRefreshed) {
-      await LoadingDialog.error(context: context);
-      return;
-    }
-    await showDialog<void>(
+    final Product inputProduct = _nutritionContainer.getProduct();
+
+    final bool savedAndRefreshed = await ProductRefresher().saveAndRefresh(
       context: context,
-      builder: (BuildContext context) => SmoothAlertDialog(
-        body: Text(AppLocalizations.of(context)!.nutrition_page_update_done),
-        actions: <SmoothActionButton>[
-          SmoothActionButton(
-              text: AppLocalizations.of(context)!.okay,
-              onPressed: () => Navigator.of(context).pop()),
-        ],
-      ),
+      localDatabase: localDatabase,
+      product: inputProduct,
     );
-    Navigator.of(context).pop(true);
-  }
-
-  /// Saves a product on the BE and refreshes the local database
-  Future<bool> _saveAndRefresh(
-    final Product minimalProduct,
-    final LocalDatabase localDatabase,
-  ) async {
-    try {
-      final Status status = await OpenFoodAPIClient.saveProduct(
-        ProductQuery.getUser(),
-        minimalProduct,
-      );
-      if (status.error != null) {
-        return false;
-      }
-      final ProductQueryConfiguration configuration = ProductQueryConfiguration(
-        minimalProduct.barcode!,
-        fields: ProductQuery.fields,
-        language: ProductQuery.getLanguage(),
-        country: ProductQuery.getCountry(),
-      );
-      final ProductResult result =
-          await OpenFoodAPIClient.getProduct(configuration);
-      if (result.product != null) {
-        await DaoProduct(context.read<LocalDatabase>()).put(result.product!);
-        return true;
-      }
-    } catch (e) {
-      //
+    if (savedAndRefreshed) {
+      Navigator.of(context).pop(true);
     }
-    return false;
   }
 }