How Deja Vu Works

"Have you ever visited a store for the first time and had it feel eerily familiar? Or maybe you're deep in conversation with a friend and you suddenly get the feeling that you've had the exact conversation before, even though you know that you haven't. If you've ever found yourself in either of these situations, you've experienced déjà vu. Sixty to 70 percent of us admit to getting this feeling at least once in our lives."

[via how stuff works]