A femtosecond is one quadrillionth of a second. Or to put it another way. A femtosecond is one millionth of one billionth of a second. A femtosecond is to a second what a second is to 32 million years. There are more femtoseconds in a single second than there are hours passed since the Big Bang. Fact, eight times more. In a femtosecond, light travels just 300 nanometers. The femtosecond laser shoots pulses at femtosecond intervals. And that lets us observe fast-moving phenomena in physics, chemistry and more as they happen. And out in the real world, the femtosecond laser has been used in things as varied as nuclear fusion to semiconductors to LASIK. It sounds impossible. In today's video, the femtosecond laser breakthrough.