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.