Gas to solid formation is usually a result of significant temperature changes or chemical combination. These processes occur naturally and artificially. Gases combine organically with other materials to produce the processes of life, but function chemically using their characteristic chemical properties as gases. At different temperatures they're capable of different things. Chemical combination is the most common form of transformation into solids. Gases frequently combine with other chemicals to form solids.
Examples of Gas to Solid:
This diagram shows the nomenclature for the different phase transitions.