This YouTube video shows just how easy it is to build a laser microscope in your own home, with which to conduct at least rudimentary scientific observations. The best part is that the instrument can be built for only a few dollars.
Its main component is a standard, presentation laser, of the type used in conference rooms around the world. The rest of the building principles are all described in this interesting video, which also showcases some of the observations that can be conducted with it at the end.
In addition to replicating the microscope you see here, you may also want to try out different materials for the basic components, as well as different wavelengths for the main laser itself. Adjusting the distance the sample is from the wall or projection medium might also come in handy.