A femtosecond laser is a type of laser that emits pulses of light lasting just a few femtoseconds, which is one quadrillionth of a second. This incredibly short duration allows the laser to deliver high energy in a very brief time, making it useful for precise applications in various fields, including medicine and materials science. In medical settings, femtosecond lasers are often used for procedures like cataract surgery and LASIK eye surgery, where precision is crucial. In materials science, they can create intricate structures or modify materials at the microscopic level without causing damage to surrounding areas.