The aim of this lecture is to present on Bergeron Process. For air with both supercooled water and ice: (1) Amount of water vapor is in equilibrium with water (saturated); (2) Amount of water vapor is not in equilibrium with ice (supersaturated); (3) Water vapor deposits onto ice, lowering the amount of water vapor, causing evaporation of water; (4) The cycle continues – ice grows and water vanishes. Once the Bergeron Process takes place, ice becomes big enough to fall, and two additional processes occur: Riming and Aggregation.