Snow precipitation degenerates rapidly once it reaches the ground. A wide variety of particle types develop in seasonal snow covers, thus leading to a wide range of snow properties. The most common varieties of particles are shown here. The physical processes responsible for the growth and development of these particles are described in general terms, although these processes are not understood as well as the processes of crystal growth in the atmosphere. The heat and mass flows associated with the development of these crystals in the snow cover are complicated because of snow's complex geometry.