The present disclosure includes apparatuses and methods related to microcode instructions. One example apparatus comprises a memory storing a set of microcode instructions. Each microcode instruction of the set can comprise a first field comprising a number of control data units, and a second field comprising a number of type select data units. Each microcode instruction of the set can have a particular instruction type defined by a value of the number of type select data units, and particular functions corresponding to the number of control data units are variable based on the particular instruction type.