The History of String Theory

In one version of string theory, it just says that particles are point particles. That failed to explain originally the properties of protons and neutrons correctly. The first versions of string theory were intended to describe those particles which did not behave like points. All particles could be represented in this way as little vibrating strings. This was a very powerful idea because it answered some of the paradoxes between quantum mechanics and gravity. But even that was not enough to completely explain the properties of black holes. So we're still wrestling with how to think about black holes properly.