Evolutionary cell biology comes of age.

Evolutionary cell biology is emerging as a vibrant discipline, integrating comparative cell biology, evolutionary theory and modern molecular approaches to understand how cells evolve and diversify. With roots dating back to the foundational work of Darwin and Haeckel in the 1800s, the field was historically eclipsed by a focus on a handful of genetically tractable model organisms. Yet, breakthroughs in genomics, imaging, experimental evolution and phylogenetics are driving the rapid growth of the field. Modern evolutionary cell biology faces four central challenges: integrating cell biology with evolutionary theory and experimental evolution to understand both adaptive and non-adaptive processes, bridging the genotype-phenotype gap, identifying and developing new model systems beyond traditional organisms to capture the full diversity of cellular mechanisms, and integrating ecological context with evolutionary processes to understand how environmental forces shape cellular phenotypes. In this Perspective, we discuss how meeting these challenges will illuminate fundamental evolutionary rules governing cellular complexity, innovation and adaptation across the tree of life, with potential applications for predicting cellular responses to future environmental challenges.