Early detection and diagnosis of dental caries reduce irreversible loss of tooth structure, the treatment costs, and the time needed for the restoration of the teeth. Listen to your patient .... The patient will give you the diagnosis.-Sir William Osler Diagnosis is the correct determination, discriminative estimation, and logical appraisal of conditions found during the examination as evidenced by distinctive signs, marks, and symptoms. Correct treatment begins with a correct diagnosis. New detection methods have been developed to aid better diagnosis. Complementing traditional diagnostic methods with advanced, more sensitive methods will improve caries diagnostic routine and hence the dental care and treatment of patients. Modern dentistry emphasizes more on prevention, and hence the original practice for "extension for prevention" has been eschewed for a minimal intervention approach.