zeptosecond
A zeptosecond is a unit of time equal to one trillionth of one billionth of a second, or 10^-21 seconds. It is currently the shortest measurable unit of time in the scientific world. Recent experiments have been able to measure the duration of light pulses on this timescale, opening up new avenues of research in the field of attosecond science.
Scientists have now been able to measure the time it takes for an electron to leave its position in an atom, and it's in the range of zeptoseconds.