The growing interest of scientifical and pharmaceutical communities in the field of biological reactions, has led to the improvement of stopped-flow mixing system that is capable of measuring rapid kinetic reactions with a timescale in the range of 0.5 ms to minutes. The SFM-4000 stopped-flow is available for a wide range of applications, e.g protein folding/refolding, protein-protein interactions, fluorescence resonance energy transfer (FRET), ligand binding, water and ion transport in vesicles and membranes, enzyme/substrate reactions, coordination reactions in inorganic chemistry, as well as identification or capture of intermediates, and more. Moreover, some time point samples for EPR, NMR, Mossbauer or GC/MS analysis can be collected if chemical quench or freeze quench accessories are coupled with stopped-flow mixers. With the SFM-4000 stopped-flow technology, it is possible to do kinetics with a rate constant up to 3500 s with the shortest possible dead time (around 700 µs and 200 µs using optional microcuvette for the most demanding applications), the highest precision and to minimize sample consumption as much as possible.