In this talk Brian Greene, an American theoretical physicists specialising in string theory, discusses this amazingly complex part of physics. This includes a short introduction and history of string theory and the current state of affairs. As Greene discusses, string theory is one of the candidates for the ultimate theory for everything, however, we have a long way to go in order to experimentally test it. Either way, if the theory is correct or not, it offers a great intellectual challenge for both physicists and mathematicians. For more similar videos, check out the links below.