Here's a video of Brian Greene speaking about string theory:(it was recorded in 2005 so it may not be up-to-date on everything)
String theory has become one of the newest possible theories that describe the universe. The theory says that there are more dimensions than just the three dimensions that we see. I was very curious to learn more about string theory because I wanted to learn more about modern theories in physics. String theory says that as we look at the makeups of quarks, we see that inside there are string-like balls of energy vibrating at a certain frequency. Each frequency creates different quarks and thus makeup different particles. Brian Greene however says that if one does the math, string theory doesn't work out with just the three dimensions. The math supports that there are ten dimensions and one time dimension. The other dimensions are so small that we do not see them. Greene also says that the CERN-the hadron collider- is what will give us the scientific evidence that there are other dimensions. This is because when two particles collide, if we record the energy before the collision and compare it to the energy after the collision, if the energy after is less than before than the the energy must have gone to another dimension, proving string theory is possible.