Turn your iPhone into a portable microscope. Should also work for any other smartphone. All I'm doing here is placing a small lens right in front of the iPhone camera. Keep it place with some foam tape and start looking at everything! Really big!
I read about this technique here
where it was used to look at stool samples on slides (fun!), but I mostly used it to look at color slides and other flat things. Below is a video of moving a slide photo of a building in front of the lens.