Everything is made of atoms. At the centre of an atom is the nucleus made of protons and neutrons. An atom also has tiny electrons which spin around the nucleus. Electrons have a negative electrical charge, and protons have a positive charge. The electrons don't stay in one place. They move around to different atoms, so some atoms have more protons, some have more electrons. An atom with more protons is positively charged. One with more electrons is negatively charged. When the electrons pass from one atom to the next, it creates an electric current.