My research explores one of life’s deepest and oldest questions: how on Earth did cells first emerge? I am profoundly interested in the origin of self-referentiality and in scrutinizing the tangled concepts of last universal common ancestor, minimal cells, protocells and chassis cells (Xavier et al. MMBR 2014). My work has involved the comparative simulation of multiple large computational models of metabolic networks of prokaryotes, the simplest life-forms known, to identify essential and ancient metabolites, reactions and pathways (Xavier et al. Met Eng 2017; Xavier et al. PLoS Comp Bio 2018). I have also worked with phylogenomics to reconstruct deep evolutionary events including the last bacterial common ancestor (Xavier et al. Comms Bio 2021). I recently identified and investigated autocatalytic networks running solely on organic cofactors and metals as catalysts (Xavier et al. Proc Roy Soc B 2020), and am currently developing that framework in the study of the emergence of metabolism.