Acridine orange is a fluorescent dye that can be excited with blue-cyan light and upon binding do DNA and RNA it fluoresces in green and red respectively (there are of course other things that make it glow green or red). Here I added the tiniest drop (< 100 nanoliters) of an acridine orange stock solution to a drop of pond water and captured a few images I decided to share. All images were acquired with the following fluorescent setup: 450-490 bandpass excitation filter, 510 dichroic mirror and 515 longpass filter.

A paramecium I think. Plan 16/0.32

Merismopedia. Neofluar 40/0.75

Colonial algae. Neofluar 40/0.75