The concept of “thinking swarms” gives rise to some initial reflections on the history and nature of this emerging technology. It was coined to denote artificial agents that can collaborate to achieve common goals in a self-organising manner. Several definitions, biological or sociological sources of inspiration and categorisations have been suggested over the past decades. In this chapter, I provide a brief overview of various conceptualisations and definitions of swarms found in the existing swarms literature, including sources that gave rise to these conceptualisations of thinking swarms. An important concept is autopoiesis, which is a process of self-sustainment found in living entities, and that became popular in systems thinking circles. The aim was to provide the readers of this book with a concise background to better understand the context of current swarms research and development.