Eggs are round. When we put an egg in the palm of our hand, the pressure on its surface is equal, which is not enough to break the shell. Because force can be transmitted, when we pinch an egg, we will transmit the force to other parts of the egg through the liquid in the egg. Eggshell is made of calcium carbonate and has a certain hardness. Of course, if we don't hold it well, the egg will still break when we press it hard, just like when we knock the egg on the edge of the pot, it will break with a bang because of uneven force.