The presence of surface-active substances (e.g. impurities by accident or proteins, surfactants added on purpose) has dragged attention from the bulk fluid behaviour towards interfacial phenomena. This talk focuses on the effect of surfactants on the coalescence and breakage of liquid filaments. iquid breakage (from a nozzle or in the microfluidic channel) is well-known to be affected by the presence of surface active species. However, how the breakage may be affected by the surfactant concentration and/or activity is far less clear and the importance of dynamic surface/interfacial tension will be presented in this talk. Flow accompanying the coalescence of drops has received little attention in the literature. Presented studies provide a thorough insight into the bulk and interfacial flows during the coalescence of aqueous drops, in particular drops having different compositions.