Biology, in essence, is the story of life on earth. This chapter forms the basis of many other topics that arise in Biology. Living entities exhibit a set of essential characteristics that sets them apart from non-living entities. Reproduction becomes a vital process without which species cannot survive for long; it ensures continuity of species generation after generations as older individuals undergo senescence, and ultimately they die. Reproduction is a biological process of formation of new offsprings from the pre-existing organism. This phenomenon is significant in the continuity of the species, generation after generations. Typically, reproduction is observed in all living organisms from single-celled entities such as amoeba to multicellular entities of the most advanced forms such as human beings. Reproduction is carried out in two modes depending upon the participation of one or both parents. Reproduction in organisms is a vast topic that includes the process of fertilization and the formation of new individuals. The topic contains an overview of sexual and asexual reproduction in plants as well as animals. Sexual reproduction involves the fusion of male and female gametes, whereas asexual reproduction involves a single parent. The process of formation of gametes in plants and animals is described stepwise.