Nothing tangible is there. The nucleus would be too small and distant to be seen. In every atom, the nucleus is as far from the electrons as the sun is from planets of the solar system. If an atom were the size of a 14-story building, the nucleus would equal a grain of salt on the seventh floor. Solidity is an electrical illusion.
Electrons seem to be nearly nothing.
They account for only about 1 ounce of your body's weight. Yet they have terrible energy. When a violent lightning storm explodes around you, you're witnessing the power of detached electrons. When you put your finger in a light socket, you're feeling electrons. Nobody knows the reality of these building blocks.