While many of these issues and events are associated with behavior and social interaction, they are linked to physical and emotional development.
One of the first major changes experienced by adolescents is puberty. The physical developments mark the end of childhood and show the first stages of adulthood. This is the biological transitional phase of adolescence, and possibly the most visible sign that it has begun. Puberty is the period in which the individual becomes capable to sexual reproduction. However, the term is also used to refer to all the physical changes that take place in the growing individual, as he passes from childhood into adulthood. Physical changes in puberty are triggered by hormones, which are chemical substances in the body acting on specific tissues and organs. In males the major change is found in an increased production of testosterone, the male sex hormone,