An Audemars Piguet watch is basically a super cool machine that tells time using only physics instead of using batteries. It all starts with something called a mainspring, which is like a tiny, powerful coil that stores energy when it is wound up. If you have an automatic model, there is a heavy metal weight inside that spins around every single time you move your arm. This spinning motion keeps the spring tight so the watch stays powered just by you walking or moving. Then, that stored energy travels through a bunch of tiny gears that work together to move the hands on the face. To keep the watch from spinning out of control, a part called the escapement releases the energy in tiny, steady ticks. There is also a balance wheel that swings back and forth super fast to make sure the timing stays totally perfect. This constant ticking is what makes the second hand look like it is gliding smoothly instead of jumping. Some of these watches even have extra features like stopwatches or calendars that are built right into the mechanical system. Every single piece is put together by hand by experts to make sure it is super strong and accurate. It is pretty amazing how hundreds of tiny metal parts can work together to tell time without any electricity. At a recent auction the Grosse Piece model was sold for $7,700,000. The price for them can range anywhere between $20,000-$70,000,000.