According to research, the central part of an atom is highly charged, and is dense with matter. Protons and neutrons are included in the nucleus. Electrons, on the other hand, revolve around it. The nucleus of a hydrogen atom, which is supposed to be amongst the smallest, is 1.6 fm (1.6 × 10−15 m), while that of a uranium atom is 15 fm (15 × 10−15 m).