 Well, you ask a question for which I don't have a definitive answer. However, people who work in string theory, and I'm one of them, believe that the string is the smallest object. Now, let's take a look at the atom. The atom is about 10 to the minus 8 centimeters across. You got that? That is the size of an atom, about 10 to the minus 8 centimeters. But what is smaller than the atom is the nucleus. So how small is the nucleus?