Roughly 60% of the human body is made up of water, making it the most abundant substance in the body. This water is essential to nearly every bodily function — from regulating body temperature to lubricating joints, delivering nutrients, flushing out waste, and enabling cellular activity. Organs such as the brain, heart, and lungs contain even higher concentrations of water — for example, the brain is nearly 75% water. Muscle tissue also holds more water than fat tissue, which means a person's hydration percentage can vary depending on age, gender, and body composition. Water also plays a crucial role in blood circulation, digestion, kidney function, and maintaining electrolyte balance. Without adequate hydration, the body becomes less efficient, leading to fatigue, headaches, impaired cognitive function, and even more severe health issues over time. Drinking enough water daily — generally 2 to 3 liters for adults — is one of the simplest yet most impactful ways to support overall health and wellness.