I love the weird stuff and I've been experimenting with things a ton lately! This trick is one of my recent experiments that I tried out and I LOVED the results from. There are a few different ways to do multiple exposures and this one is technically only one exposure although it gives you the multiple exposure look. If you haven't already, make sure that you read the "Long Exposure" tip before you go any further into this one. If you don't, I can assure you that this won't help at all.... Okay, you finished? Great! Now just like in that tip, you still have your shutter open for one second, your camera on a tripod, etc but instead of a single flash to freeze your subject in the frame you have two. Personally, I like to do this manually with a flash trigger. I take the shot, and while the shutter is open, I'll push the trigger twice so the flash freezes them twice. With some ambient light in the room, the glow will come out in between too. I know this all seems so technical and weird but I promise that experimenting with it is the quickest way to understand it! Easy peasy.