Basic superscript is between ^s:
E=mc^2^.
.
<p>E=mc<sup>2</sup>.</p>
Backslash escapes:
E=mc\^2\^.
.
<p>E=mc^2^.</p>
Spaces and formatting are allowed:
E=mc^2 or *3*^.
.
<p>E=mc<sup>2 or <em>3</em></sup>.</p>
Punctuation is ignored for purposes of determining flankingness:
E=mc^!^.
.
<p>E=mc<sup>!</sup>.</p>
Superscript can't begin or end with a space:
E=mc^ 2^.
E=mc^2 ^.
^ ^
.
<p>E=mc^ 2^.</p>
<p>E=mc^2 ^.</p>
<p>^ ^</p>