In response to Patrick Eklund Among the real-world applications of category theory, I can mention those deduced from the categorical-based methodology of "Memory Evolutive Systems" which we have been developing with Jean-Paul Vanbremeersch for the last 30 years . MES propose a model for studying evolutionary multi-scale, multi-agent systems such as biological and social systems. The main theory can be found in our Elsevier book: "Memory Evolutive Systems: Hierarchy, Emergence, Cognition" (2007), and more recent results in a series of papers (cf. the references on my site http://ehres.pagesperso-orange.fr (or on Research Gate at my name Andree Ehresmann). In particular MES lead to realworld applications in: - Biology and Medecine (e.g. aging theory for an organism), - Neurosciences: model MENS studying the development of higher cognitive processes, up to consciousness, and creativity, - Anticipation and future studies, - Innovation and design. Best regards, Andree [For admin and other information see: http://www.mta.ca/~cat-dist/ ]