Stirred reactors are the most commonly encountered chemical reactors. However, the model of the ideal stirred tank only applies, if at all, to laboratory-scale devices. Industrial-scale reactors, on the other hand, exhibit concentration and temperature differences, which can be significant for the chemical reactions. This fact often leads to lower yields and selectivities in the production reactor. For the interplay of chemical reactions and mixing processes, characteristics of the mixer such as homogenization, heat, and mass transport, as well as the specifics of multiphase reactor operation, are essential.