Until 1932, it was thought that the nucleus only consisted of protons and electrons. It was discovered then that there are not electrons but neutrons in the nucleus besides the protons. (The renowned scientist Chadwick proved in 1932 the existence of neutrons in the nucleus and he was awarded a Noble Prize for his discovery). Mankind was introduced to the real structure of the atom only at such a recent date.
We had mentioned before how small is the nucleus of the atom. The size of a proton that is able to fit in the atomic nucleus is 10-15 metres.
You may think that such a small particle would not have any meaning in one's life. However, these particles that are so small as to be incomprehensible by the human mind form the basis of everything you see around you.
