The lag (latency) time (LT) is known in dermatology clinic as an asymptomatic period till the development of skin eruptions. In the laboratory, the LT might determine the interval from \zero" point until the peak(s) of changes in measured laboratory parameter during the performed test. This paper discusses methodological and technical aspects of precise measurement of the LT in the living healthy and pathological skin by laser and optical technologies through clinical and experimental applications in dermatology. Based on a dynamics approach to measure, calculate and interpret the LT in blood and in interstitial fluid compartments of the skin tissue, this method has a potential to promote deeper understanding of the role of complex dynamic processes in the skin at a level of a molecule, and/or an organ in a whole organism. The method of the LT measurement in vivo also promotes new understanding of (patho)physiological, diagnostic and pharmacological aspects of certain dynamic skin lesions and dynamic complex processes that happen in the skin. Utilized laser and optical techniques showed high reliability and objectivity in collecting data from rapidly changed skin lesions and processes, demonstrating the LT measurement as a very easy-to-use calculation procedure with high informativity, which is extremely important for the clinical and laboratory environment.