The chapter presents five types of functional concepts, with an example of each type. These are (1) prototypes, (2) classifications and categories, (3) process concepts, (4) systems concepts, and (5) germ cell concepts. Each type of functional concepts has its own specific strengths and affordances. In other words, one type is not “better” or “more advanced” than the other. However, many complex activities would benefit from making use of the complementarity of different types of functional concepts. Tools become powerful when they become an interconnected instrumentality. Recognizing the different conceptual resources – and conceptual gaps – in an activity system opens up the possibility of building a conceptual instrumentality, that is, a repertoire of different but complementary and interconnected types of concepts available for the practitioners for conducting and developing their collective activity. In particular, the germ cell concepts have potential that has so far remained largely unrecognized in organizations. This is demonstrated with the help of the example of the concept of knotworking.