The main objective of the experiment is to design a procedure for measurement of membrane fluidity, i.e. fluorescence anisotropy, on living yeasts at 4°C and 22°C. For this purpose, we will performed preliminary tests to evaluate the technical environment necessary with the TELEMOS microscope such as convenient objectives, controlled temperature stage using Peltier effect, polarizer rotation, software image acquisition procedure, etc. Various staining conditions with TMA-DPH and Laurdan dyes have also to be tested. During this beamtime, we will expect a set of good quality parallel and perpendicular images convenient for fluorescence anisotropy calculation.