The kidneys are the organs in the human body primarily responsible for filtering blood. They remove waste products, excess substances, and toxins from the blood, regulating fluid balance, electrolytes, and blood pressure in the process. Each kidney contains around a million tiny filtering units called nephrons, which perform this vital function. The filtered waste is then excreted as urine. In addition to waste filtration, the kidneys also play a role in producing hormones that regulate various bodily functions, including red blood cell production and maintaining bone health.