Look at this photo printed on algae in a petri dish
by Xeni Jardin from on (#53991)
Okay, now THAT is a selfie.
This is such a cool photography/biology experiment.
Says IMGURian @MxMarx, I put a petri dish filled with algae under my enlarger and left it on for a week. The algae grew thicker and greener where the image was brighter, so it formed a positive image in the petri dish!"
Scroll through the entire gallery to see how this was done.