Genetics is an indispensible chapter in a textbook of growth. The command of genes is translated into growth of the organism. This chapter outlines the basics of genetics from DNA structure, describing the process of transcription and translation and regulation of gene expression, to modes of inheritance. Twin studies form an important research tool in analysis of inherited characteristics. There is an excellent discussion on molecular aspects of growth and growth factors. Various inherited disorders are discussed including cleft lip and palate and various syndromes. This chapter is extremely informative to an astute academician.