A variety of powerful techniques for monitoring and analysing events during signal transduction at the single cell level are described in this lab manual. An introductionary section on cell handling includes guidelines for constructing a perfusion chamber. A main section of the book presents protocols on fluorescence techniques such as flow cytometry, microfluorescence, ion imaging and confocal microscopy. The electrophysiological section illustrates multiple applications of the patch-clamp technique in various cell types from both animals and plants. Emphasis is put on calibration and validation of the different techniques to measure changes of membrane potential, and intracellular ion concentration or pH.