Variability in brown dwarfs: Atmospheres and transits

We have obtained series of continuous differential photometry in the J and K-S bands for several L-type dwarfs. We intend to search for photometric variability in order to: investigate the variability amplitude associated to atmospheric changes in time-scales from minutes to several hours, investigate rotation periods through light curve modulation due to superficial inhomogenities, set constrains on the frequency of flares in these fully convective objects, search for transits of brown dwarf and planetary companions in very close orbits (including habitable zones). First results obtained for the brown dwarf 2M1146+22 are presented.