This is a structure for build a microscope by using a drop of clear water instead of a glass lens. The small water drop works as a spherical lens with a large magnifying power.

I use the drop in the output of a common syringe and a laser of 5mW in the range of 405nm but other colors work in the same way

Original project: http://www.szertar.com/letoltheto/lezermikroszkop.pdf