eng Science and Education Publishing Biomedical Science and Engineering 2373-1265 2016-09-22 4 1 23 30 10.12691/bse-4-1-3 BSE2016413 article Yasutomo Nomura ynomura@maebashi-it.ac.jp 1 Department of Systems Life Engineering, Maebashi Institute of Technology, Kamisadori, Maebashi, Japan Fluorescence correlation spectroscopy is a powerful method in clinical laboratory where a lot of samples of patients will be determined because it enables to measure concentration and molecular weight of tested molecules without any physical separation steps. Nevertheless it may not yet be used as widely as one expected. The reason is that it is likely to be difficult for many users to understand the theoretical background. In this method, the users measured intensity fluctuation of fluorescence resulted from the molecules entering and exiting tiny volume element, namely Brownian motion in solution. Using the time series data of fluorescence intensity, the autocorrelation function was calculated. When the function was fit to the analytical model derived from diffusion theory, concentration and molecular weight of fluorophores were obtained. This minireview described the theoretical background of Brownian motion, physical meaning of the correlation analysis, and its usage properly dependent on samples from homogeneous solution to inhomogeneous cell. Furthermore the recent advances are also outlined. http://pubs.sciepub.com/bse/4/1/3/bse-4-1-3.pdf fluorescence correlation spectroscopy Brownian motion diffusion theory diagnosis clinical laboratory