Adolescence spans from age 11 or 12 to 17 or 18, encompassing a duration of six years. The phase from 11/12 to 14/15 years old is often referred to as junior high school for individuals. This three-year period marks an acceleration phase of physical development, all bodily systems and structures rapidly develop and progressively mature. The stage from 14/15 to 17/18 years old is also referred to as early youth, coinciding with high school attendance. Following successive developmental stages, individuals in early youth have achieved physiological maturity and are nearly at the adult intellectual level, exhibiting more abundant characteristics in personality and other psychological attributes. However, the prevalence of subclinical psychiatric symptoms is higher in late childhood and adolescence compared to adulthood. Adolescence, marked by swift physical transformations, hormonal shifts, brain restructuring, and a transition in social roles, represents a high-risk period for mental and emotional disorders. This review systematically explores the sexual development, hormonal changes and physical development, neurodevelopment and effects of hormones in adolescences, describing the physiological characteristics underlying of susceptibility to mental and emotional disorders during adolescence.