Abstract The kinetics of chemical reactions at equilibrium can be investigated in samples of very small size with a giant laser pulse shifting the state of equilibrium by a temperature jump. The output of a Q-switched neodymium laser is fired into a microcavity of 5 μl. The solvent, which absorbs part of the laser energy, is heated instantaneously and the kinetics of the chemical processes leading to the new state of equilibrium can be followed up. The principles of the present design are based on the particular properties of a giant laser pulse—high energy and short duration, small beam divergence, emission at wavelengths where many solvents already absorb—and permits thereby (a) a very high time resolution, (b) a very small sample size (⩾ 5 μl), and (c) the use of polar as well as apolar solvents, since heating occurs by means of electromagnetic energy absorption instead of Joule-heating due to ionic conduction. The design of the instrument is such that reaction kinetics even in such integrated biological structures as single cells or cell organelles can be studied.