One of the most interesting sources of gravitational waves are processes in the very early universe. Phase transitions such as the splitting of what is called the electro-weak force into electromagnetism and the weak nuclear force, whip-lash processes involving cosmic strings and a number of even more exotic processes should lead to gravitational waves that could be explored with the next generation of detectors. In this way, scientists are planning to eavesdrop on events taking place less than a trillionth of a trillionth of a second after the big bang.