Uh oh, you were unlocking your door and the key broke off in the lock! Here’s a trick that locksmiths use: first, as long as there is a visible edge of the key, dab a tiny bit superglue onto the part of the key that is NOT stuck in the lock. Then hold and press against the piece that IS stuck in the lock. Let this dry for about 3 minutes. Then, slowly pull the key toward you. Hopefully, the glue has fused the 2 pieces together so you can extract the key. If this works, run, don’t walk, to the nearest place to get your key replaced!