Dental caries is a multi-factorial disease. The process by which tooth can be destroyed in the oral cavity, which is indestructible otherwise, is very difficult to understand. Till today, no single theory can explain the phenomenon of caries. Numerous references of dental caries, including early theories to explain the mechanism of caries have been found in history books. The changing nature of the disease process has therefore accentuated the need for more precise detection methods. Unfortunately, because of the nature of disease process in the past, the currently available diagnostic methods have limitations due to which the dynamic nature of lesion is not measured.