Hormones are extracellular chemical messengers that, in response to a particular signal, endocrine glands or diffusely distributed specialized cells, secrete into the blood which carries them to other places in the body where are target cells they operate. They have specific receptors that can bind only certain hormones. There are many different types of hormones that act on different aspects of body functions and processes: maintaining blood osmolarity and blood sugar, regulation of metabolic function (monitoring the speed of chemical reactions, mass transport through membranes and other metabolism features like excretion or growth), control of sexual activity and reproductive cycle and shaping behavior. This work provides a short overview of sex hormones and the impact they have on shaping behavior in mammals, with emphasis on humans. Sex hormones are essential to the development and morphological differentiation of the sexual organs and sexual differentiation of the brain, and for activation and regulation of male and female sexual behavior and cycles, as well as for determinants and implementation of some factors of general behavior.