The Sheldon body types, developed by psychologist William Sheldon in the 1940s, categorize human physiques into three main types: ectomorph, mesomorph, and endomorph. Ectomorphs are typically slim and lean, with narrow shoulders and hips. Mesomorphs have a muscular build, broad shoulders, and a naturally athletic appearance. Endomorphs tend to have a rounder physique, with wider hips and a higher percentage of body fat. Sheldon believed that these body types could be linked to personality traits and temperaments. For example, ectomorphs are often described as introverted and sensitive, while mesomorphs are seen as assertive and energetic. Endomorphs may be more sociable and relaxed. However, it's important to note that most people exhibit a combination of these body types rather than fitting neatly into one category.