  We have investigated the time variations in the light curves from a sample of
long and short Fermi/GBM Gamma ray bursts (GRBs) using an impartial wavelet
analysis. The results indicate that in the source frame, the variability time
scales for long bursts differ from that for short bursts, that variabilities on
the order of a few milliseconds are not uncommon, and that an intriguing
relationship exists between the minimum variability time and the burst
duration.
