An atom is like a tiny little ball. Inside the ball, there are even smaller balls called protons and neutrons. These balls stick together in the middle of the atom. Around the outside of the atom, there are even smaller balls called electrons that fly around the big ball like tiny little bugs. Each kind of atom is different because it has a different number of protons, neutrons, and electrons. This is what makes everything around us different. Like your toy car is made of different atoms than my pencil.