FROG is the gold standard for ultrashort-laser-pulse measurement.
Perhaps the best feature of FROG is its over-determination of the pulse: it is a 2D array of points even though the pulse is only 1D. As a result, agreement between the measured and retrieved traces tells us that the measurement was made well and the the pulses (if the measurement averaged over many of them) were stable.
The pulse shown here was a record: the shortest event ever created. But it's since been beaten (and that pulse was also measured using FROG).