Abstract: The invention relates to a procedure and a micromixer for mixing at least two fluids. The aim of the invention is to reduce the mixing time of the micromixer compared to micromixers known to the art while maintaining high mixing quality and small structural dimensions. The inventive procedure is characterized by the following steps: a plurality of separated fluid currents of both fluids are brought together and alternately adjacent fluid lamellae of both fluids are formed: the combined fluid currents are carried away and a focused total fluid current is formed; the focused total fluid current is fed as fluid jet into an expansion chamber; and the resulting mixture is drawn off. The micromixer comprises a plurality of alternately adjacent fluid channels which open into an inlet chamber. A focusing channel is in fluid connection with said inlet chamber and opens into an expansion chamber.