Abstract: The invention pertains to a method for the study of the behaviour or detection of cells, organites or cellular fractions, possibly present in a medium.It comprises providing said medium with the essential nutrients to promote the activity of the said cells, organites or cellular fractions, if any, as well as with an "electron transporter" such as lipoic acid which is liable of forming a redox system and of intervening in one of the metabolic routes involved by the above said activity, particularly growth of cells.The method of the invention then further comprises measuring and detecting a possible modification of the relative proportions of the oxidized and reduced form of the "electron transporter". The time required for such modification to possibly take place, as well as other parameters of the reaction can then be correlated to the presence in the medium concerned of a cellular activity or analogous.