Free Fat Mass (FFM) in children refers to the portion of Body weight that encompasses all non-fat tissues, including muscles, bones, organs, and fluids, excluding fat mass. It plays a crucial role in determining a child's metabolic health, growth, and overall well-being. During childhood, FFM serves as a significant indicator of physical development and fitness. As children grow, their FFM tends to increase, influenced by factors such as genetics, nutritional intake, physical activity levels, and hormonal changes associated with puberty. Understanding and monitoring FFM in children is essential, as it helps assess Body Composition beyond just Body weight or Body Mass Index (BMI). Higher FFM levels typically correlate with better strength, endurance, and metabolic health. Adequate FFM in children is essential for proper growth, bone development, and overall metabolic function. However, imbalances in FFM, such as insufficient muscle mass or disproportionate growth of certain tissues, might signal underlying health concerns, such as malnutrition, hormonal imbalances, or certain medical conditions. Accurate measurement and evaluation of FFM in children often involve specialized techniques like dual-energy X-ray absorptiometry (DEXA), bioelectrical impedance analysis (BIA), or anthropometric measurements. These methods help healthcare professionals gain insights into a child's Body Composition and tailor appropriate interventions, such as nutrition plans or exercise regimes, to support healthy growth and development.