This project consists in writing a monograph about the irreducible and pervasive complexity of the natural world (the biological world, in particular), and about the importance of becoming increasingly aware of this intrinsic complexity, in continuous development and evolution (more so when combined with the artificial worlds recently created by humans), if we are to handle adequately future challenges for science and society. Although the core of the essay will be focused on the definition of minimal life and the long and amazingly convoluted process that is required for its primordial emergence, which will support my main ‘take-home’ message, the topic will be conceived within a more general framework, covering aspects that have to do with the special relevance of scientific knowledge and its relationship with other types of human knowledge. Therefore, the essay will have a strong trans-disciplinary vocation, putting together insights from physics, chemistry and biology, for obvious reasons, but also demonstrating how that necessary work of integration, in practice, requires the elaboration of theoretical models and conceptual tools/languages that come from other fields, like computer science, or philosophy itself. In this wider context, a new type of scientific realism will be advocated, according to which methodological pluralism, multi-causal and multi-level approaches, together with a much more committed social engagement in scientific practices and decision-making, will be claimed as critical to face upcoming problems for our species.