To study the tropical climate, one can study radiative-convective equilibrium in such a doubly periodic box. Typically, one fixes the surface temperature and assumes that the surface is water-saturated (mimicking conditions over the ocean). One then turns on the Sun, evaporates water, and allows the model fluid dynamics, radiation, and thermodynamics to redistribute energy and generate a hydrological cycle with precipitation balancing evaporation. One may be interested in how the relative humidity or cloud distributions are maintained in such an ideallized horizontally homogeneous system, or one may focus on the (related) question of the how the convection is organized. Moist convection, dominated by phase changes, has many strange and unfamiliar aspects that are usefully isolated in these idealized geometries. One of the first simulation of radiative-convective equilibrium, and (to our knowledge) the first with radiation fully interactive with the model-generated clouds (albeit with one horizontal dimension only), was produced at GFDL in 1993.