Summary

Based on this article from Make. I didn't really invent this, though my version is slightly different and 3d-printed.

You build a base around the lens of a laser pointer, and you have a ridiculously cheap, portable, and decently rugged microscope!

Instructions

CAD Model

I designed a base located here at Onshape. The sketch from that model can serve as a machining or drilling template for your acrylic pieces. I've uploaded the latest sample, but the Onshape document gives you parametric access if you want to, say, change screw inner diameter to imperial units or something silly.

Parts List

Obviously, if you change out the screws to being something other than metric, M6, you'll need to change the hex nuts, washers, and wingnuts, and likely the compression springs as well

M6 Socket Cap Screw - 100mm long *See note below
M6 Hex Nut
M6 Washer
M6 Wingnut
Steel Compression Spring

If you purchase from those links, you're going to have spares... lots of spares. But they're really nice.

Smartphone Microscope