I know the basics. A liquid polymer resin is hardened by a laser or light beam. However, I don't understand how the laser can only hit the surface and harden 0.001mm of that surface, without penetrating deeper into the liquid. How is this possible?

Also, is the laser a single point, whereas it only cures the resin one tiny dot at a time, or is it curing it an entire layer at a time?

I'm just wondering this stuff. Maybe I sound stupid, but I need to know, because its been bugging me