What causes déjà vu and why does it feel so weird?

You get déjà vu when your brain thinks it’s seeing something new, but actually remembers it from before, like when you walk into a room and think you’ve been there a million times before.

Imagine you're playing with blocks. You stack them up in a certain way, then later you see someone else do the exact same thing, but you didn’t realize they were copying you. Your brain goes, “Wait, I just did that!”, and that’s déjà vu.

Your brain has two parts working at once: one is thinking about what's happening right now, and the other is remembering something from earlier. Sometimes those two parts get mixed up, like when you're halfway through a song and suddenly think you’ve heard it all before, even though you haven’t.

It’s like wearing your favorite hat, then seeing someone else wearing the same exact hat across the room. You know it's not magic, it's just your brain getting confused for a moment!