Check this out:
That is actual metal, spontaneously sprouting a type of facial hair known as tin whiskers.
While tin whiskers are very cool (not to mention being an awesome name for a band), their consequences are pretty serious. Because they can cause electrical shorts, they’re one of the weirder reasons circuit boards fail. They can also cause batteries to short – whiskers sometimes punch through the separators between anode and cathode, creating a direct, and far less useful, pathway for electron flow. This has been a bit of an issue in development of advanced batteries, like those used to power Hybrid and Electric Vehicles.
If you’re interested in learning more, NASA’s tin whisker page is full of great information. Check it out!