Which material do kidneys remove in particular?

Explanation

The kidney is an organ that removes waste from the body. All vertebrates and some invertebrates have kidneys. They are also important for regulating electrolytes. Human kidneys are 10-12 cm long and we have one on the left, and one on the right. Although the body has two kidneys, it is entirely possible to survive with just one. Thus, having two is a kind of 'double-insurance' which makes the body able to survive in case one kidney suddenly fails.