Have you ever had that weird feeling that you've experienced the same exact situation before, even though that's impossible? Sometimes it can even seem like you're reliving something that already happened. This phenomenon, known as déjà vu, has puzzled philosophers, neurologists and writers for a very long time.
Starting in the late 1800s, many theories began to emerge regarding what might cause déjà vu, which means "already seen" in French. People thought maybe it stemmed from mental dysfunction or perhaps a type of brain problem. Or maybe it was a temporary hiccup in the otherwise normal operation of human memory. But the topic did not reach the realm of science until quite recently.
