Focus stack—
Frames captured0
Sharp coverage—
This is the thing a hand lens cannot do. At this magnification the depth of field is a fraction of a millimetre, so any single image has one sharp plane and blur either side. This takes a series at different focus depths and keeps, for every pixel, whichever frame was sharpest there — so the whole broken surface is sharp at once.
Scale
A coin, a bank card, an AA cell — anything whose size is fixed by somebody other than us. Tap across it, then say what it is. A typed field of view is an estimate and the result will say so.
Works on any phone. Where the browser lets the page drive the lens — most Android phones — the stack is automatic. On an iPhone you tap to focus and add frames yourself, and the merge is identical.