Dinosaurs, like many reptiles today, buried their eggs in warm soil or in piles of decomposing vegetation. Dinosurs did not sit on a nest like birds. The heat from the soil or decomposition incubated the eggs and the embryos matured. Some scientists think the mother dinosaur stayed close to the nest to protect the eggs or adjust the rotting vegetation to provide a correct temperature. At some point in their development the embryos broke out of the eggs, like chicks do, and started off on their own.