Origins of life: the possible and the actual.

The questions of how life forms, whether life is an inevitable outcome and how diverse its presentation could be remain some of the most profound in science. Investigations into the origin of life confront key issues such as uncovering key constraints and universal features of life, the plausibility of alternative biochemistries and the transition from purely chemical systems to information-bearing, evolvable entities. Many of these issues can be associated with early cell formation and evolution. Thus, protocellular systems have emerged as a key focus of study. Here, the community can ask questions about physical constraints and the co-evolution of energy, matter and information. The pursuit of these answers spans a wide range of disciplines, including geochemistry, statistical physics, systems and evolutionary biology, artificial life, synthetic biology and information theory, and reflects the inherently interdisciplinary nature of origin-of-life research. This article surveys key theoretical frameworks and experimental approaches that have shaped our current understanding, while outlining the major unresolved challenges that continue to drive the field forward. It also summarizes and contextualizes the articles in this special issue that address these questions.This article is part of the theme issue 'Origins of life: the possible and the actual'.