Many times throughout this book, the reader encounters the motif of understanding, cooperation, and (mutual) manipulation. These conceptions are not self-evident in the original framing of the Darwinian paradigm, even if competition (struggle for life) amongst life forms is one of centerpieces of the teaching and can be easily extended even to cooperative behavior (as evidenced in The Descent of Man). In brief, the role of communities has, in our opinion, been largely underestimated: the individual or its genes has been given priority. The chapter first introduces the game theory model for cooperative strategy payoff and its comparison with the view of the authors. The chapter offers an overview on various forms of symbiotic interactions such as intimate endocytobiosis (as in case of protists) or cohabitation of two partners who consistently remain ‘for their self ’ by thoroughly maintaining their cell closures as is case of lichens, squids and coral, as well as mycorrhiza and endophytic fungi. The chapter further discusses the intracellular symbioses in multicellular organisms (mycetomes, nitrogen-fixing modules of legumes). It concludes with the case of mycorrhiza and bacterial consortia.