Found this sad sea urchin washed up on the beach last week:

Here is one of its scary looking spikes:

Was hard to see anything with the usual Foldscope set up. So after digging around a bit on the Microcosmos site, I found this post:

A simple hack for reflection/epi-illumination using the foldscope

Using a similar set up with an LED and a battery, inserted from one side of the stage:

I got a lovely view of the spike!

This post is open to read and review on The Winnower.