  Recent discoveries of variable brown dwarfs have provided us with a new
window into their three-dimensional cloud structure. The highest variables are
found at the L/T transition, where the cloud cover is thought to break up, but
variability has been found to occur also for both cloudy L dwarfs and (mostly)
cloud-free mid T dwarfs. We summarize results from recent HST programs
measuring the spectral variability of brown dwarfs in the near-infrared and
compare to results from ground-based programs. We discuss the patchy cloud
structure of L/T transition objects, for which it is becoming increasingly
certain that the variability does not arise from cloud holes into the deep hot
regions but from varying cloud thickness. We present a new patchy cloud model
to explain the spectral variability of 2MASSJ21392676+0220226. We also discuss
the curious multi-wavelength variability behavior of the recently discovered
very nearby early T dwarf WISE J104915.57-531906.1B (Luhman 16B) and the mid T
dwarf 2MASS J22282889-431026.
