Do you ever feel like you're living in future land?

I'm happy to admit I'm not down with the kids. My own kid is more than enough to wear me out, thanks. But when a DJ friend of mine showed me this:

......I kinda choked on my coffee and covered him in it. 'Cos that looks damn like Tupac Shakur up there on stage, and this was last year.

How the hell was that done?  Were the words encoded in the coffee I sprayed across the room. See I'm a technology geek, and I know that light doesn't just stop or change direction without a damn good reason.

Like any brilliant piece of magic, knowing how it's done can spoil it. But if you want to know (and there's a rumour Tupacs going on tour), read on: It's actually a 21st century upgrade to a very old technology.....