Within the last 20 years, the string theory has become the leading theory to describe the fundamental particles and forces in nature. The string theory is based on the premise that at an extremely small scale, particles are actually one dimensional extended objects. All objects such as quarks are made up of these strings. Different objects appear depending on the movement of the string particle. As of yet, there is no evidence for or against this theory, but hopefully soon results from experiments using large particle colliders may confirm or disprove this theory.
Quarks are the particles which make up protons and neutrons.
To find quarks, physicists smashed a proton and antiproton together. This caused them to break into bits and fly off in different directions. The particles left trails, which were analyzed by computer. All the quarks also have different masses. Up and Down are the lightest, while Top is by far the most massive.