You know the kidney is an organ but there another behind kidneys?

There is no other organ behind the kidneys. The kidneys are located in the retroperitoneal space, which is the area behind the peritoneum, which is the membrane that lines the abdominal cavity. The kidneys are located on either side of the spine, with the right kidney being slightly lower than the left kidney. The kidneys are responsible for filtering waste products from the blood and producing urine.