The primary composition of the human body is water, which accounts for about 60% of an adult's body weight. Other key components include proteins, lipids, carbohydrates, and nucleic acids. Water plays critical roles in maintaining body temperature, facilitating metabolic processes, and transporting nutrients. Proteins are essential for building and repairing tissues, while lipids provide energy storage and structural integrity to cell membranes. Carbohydrates serve as a quick energy source, and nucleic acids, like DNA and RNA, are vital for genetic information and protein synthesis. Together, these components are crucial for maintaining overall health and function.