$35 lens turns any smartphone into a powerful microscope

If you have access to petrographic thin sections, cross polarisation yields vivid, changing, kaleidoscopic colours worthy of a 60s light show: https://www.shutterstock.com/shutterstock/photos/395356066/d...

If you don't, the machinery (and space to set it up) may set you back more than $35: https://www.lakeheadu.ca/sites/default/files/uploads/3143/ge... (cheap but large) https://www.wardsci.com/store/product/8877688/ingram-ward-co... (small but spendy)

[In the opposite direction, I once bought a USB microscope and discovered that, when focussed at infinity, it turned into a webcam without an IR filter.]

Lagniappe: https://www.youtube.com/watch?v=ncHctrAluLM

At $35, it is much less expensive than I anticipated. Still interested in seeing third party reviews.

A couple years ago I got a phone camera lens kit in hopes of augmenting my cellphone photography and it was less than stellar.