Convective clouds play a critical role in climate. These clouds are typically parameterized in atmospheric models by assuming the clouds to be embedded in a homogenous environment. One of the key ingredients of this formulation is prescribing the rates of mass exchange between the clouds and their environment by parameters called entrainment (flux into cloud) and detrainment (flux from cloud). The mass exchange controls vertical profiles of temperature, moisture, and liquid water within clouds, and consequently also their vertical extent. In spite of their critical importance in climate models, these parameters are not objectively well determined and so are currently simply tuned.