The experiments at LEP showed what was happening in the universe when it was less than a nanosecond old. They revealed a state of symmetry where the energy from the still-hot Big Bang is congealing into particles of matter and antimatter in perfect balance. In all experiments performed so far, under these conditions there is no preference for one form (such as matter) over the other. This is utterly different from what we see today, billions of years after the Big Bang, where the universe is dominated by matter and radiation to the exclusion of antimatter. The cause of this asymmetric situation is one of the greatest unsolved mysteries in science.