I stumbled across the OpenFlexure project a while back and was immediately intrigued by the idea of a fully 3D-printed microscope. I was skeptical you could print a microscope that would perform well. 

I printed their basic v7 microscope. No lasers (yet), but it has been impressive. It uses the Raspberry Pi Camera v2 and connects  to your network. So far, I’ve used it to examine a few prepared slides and discovered some paramecium swimming around in pond water. The software is amazing. Once connected to the network you can log in from other computers on your network through a web interface. You can control all the axes in software and take images. It also has an option to take multiple photos at different focal lengths which you can stack in software to create deep imagery that is in focus. 

The OpenFlexure community has  a huge number of mods. Next, I'll experiment with different types of illumination, and eventually build another one of their microscope designs to use for fluorescence imagery. 

All in this cost me about $275 USD to build and does more than any microscope I've ever used.