The organ responsible for filtering the blood in the human body is the kidney. Each kidney contains approximately a million nephrons, which are the functional units that filter blood, remove waste products, and regulate electrolyte balance. The kidneys also play a critical role in blood pressure regulation, fluid balance, and acid-base homeostasis. Through the formation of urine, the kidneys excrete waste materials while reclaiming necessary substances back into the bloodstream. Proper kidney function is vital for maintaining overall health.