Observations of directly imaged and transiting exoplanets and brown dwarfs revealed the presence of condensate clouds that strongly influence the energy transport through the planetary atmospheres. The clouds also impact the evolution of the atmospheres as well as the emerging spectra. The structure and properties of these cloud layers remain mostly unknown and pose one of the outstanding challenges in understanding ultracool atmospheres.
I will introduce a new observing technique in this field, rotational phase mapping, that provides an exciting look into the atmospheres and clouds of exoplanets and ultracool brown dwarfs. I will discuss multiple Hubble and Spitzer programs, including a Cycle-9 Spitzer Exploration Science program, that apply this new technique to a large number of targets and provide spatially resolved cloud maps. The data paints an exciting and often surprising picture on ultracool photospheres. I will show that the success of this observational technique also motivates future applications on directly imaged gas giant exoplanets and super-earths, whose photospheres and surface can be mapped in the near future.