Below is an instruction from Human. Write a response.
    ### Instruction:
    What is (are) Kidney Stones in Children ?
    ### Response:
    Four major types of kidney stones occur in children:
                
- Calcium stones are the most common type of kidney stone and occur in two major forms: calcium oxalate and calcium phosphate. Calcium oxalate stones are more common. Calcium oxalate stone formation has various causes, which may include high calcium excretion, high oxalate excretion, or acidic urine.
    