Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) What I need to know about Kidney Stones ?
    ### Response:
    Doctors have found four main types of kidney stones:
                
- The most common types of stones contain calcium. Calcium is a normal part of a healthy diet. Calcium that is not used by the bones and muscles goes to the kidneys. In most people, the kidneys flush out the extra calcium with the rest of the urine.
    