This unit refers to the basic question of life; “Where did we come from?” At the introductory level, we start with the history of earth at the chemical level and then take it to the origin of life. It is a very important topic to understand how the atoms contribute to the formation of molecules, then macromolecules, the cells, and the organisms. It continues with the forms of energy such as kinetic, potential, and chemical and the transformation of energy to be used by the organisms for their survival.