See this bike helmet? No? That's because it's invisible. No, really, it is: that hefty collar that the bicyclist (or whatever) in the above pic is wearing contains a helmet-shaped airbag that deploys on demand to save your skull, and spends the rest of its time out of the way and looking fashionable.

There's still an awful lot that's not understood about how complex biological systems (like our bodies) really work. Part of the problem is that we can't just go look, since the only way to really see inside a brain (for example) is to cut it open, which by definition destroys its structure. Japanese scientists have a better idea: just turn everything transparent.

Big waves can be bad news for coastal areas, and over time, even moderate wave action can erode beaches down to nothing. In one of those schemes that sounds crazy but isn't, Chinese researchers have developed a system that uses concrete cylinders to render coastlines effectively invisible to incoming waves.

Who would have thunk that the secret to invisibility might be within that of the multi-armed squid? The U.S. Navy is pumping $5 million into a team of scientists at Duke University over the next five years to see if they can tap into the squid's special "light sensitive organs" for use on the battlefield.