3D Printed magnifying glass!? This is a project I’ve wanted to try for ages and I’m so pleased with how it turned out, check out the video https://youtu.be/jLYyXJc0Lks
Wow, next up: fully 3d printed telescope
@Matthew_Del_Rosso good idea.
Or print a microscope 
A Fresnel lens might be interesting to see if it can be aligned with the layer stepping to come out “printer perfect”