Identification of the main crystal components of urinary stones is very important for the diagnosis of clinical urolithiasis. In fact, only when the composition of stones is clearly identified, it is possible to treat the stones at their root and prevent their recurrence. There are more than 10 clinically important crystal components, which can be summarized into five major categories according to their chemical composition: calcium oxalate, calcium phosphate, uric acid, ammonium magnesium phosphate, and cystine. Most stones are mixed stones, containing more than two components, with one of them being the main body of the stone. Calcium stones (including calcium oxalate stones, calcium phosphate stones, and a mixture of both) are the most common, accounting for nearly 90% of all stones; uric acid stones occur mostly in men; magnesium ammonium phosphate stones are mostly found in women; and cystine stones are more prevalent in children. In addition, stones of other components, such as calcium carbonate stones and silica stones, are rare.