2016 marks the centenary of the death of Elie Metchnikoff, whose 19th-century studies of starfish larvae led to the description of immune cell phagocytosis. This discovery, along with follow-up studies, earned Metchnikoff the 1908 Nobel Prize in Physiology or Medicine. We have come a long way since those early discoveries. A hundred years later, we now know that a wide variety of phagocytic cells—not only immune cells—play essential roles in physiological homeostasis and disease. The functions of these professional and non-professional phagocytic cells are wide-ranging, touching on everything from the clearance of pathogens to the engulfment of apoptotic cells to the trimming of neuronal synapses.To commemorate Metchnikoff’s important achievement, Developmental Cell is co-hosting with Immunity a unique Cell Symposium, 100 Years of Phagocytes (www.cell-symposia-phagocytes.com), near Messina, Italy, where Metchnikoff first made his discovery. Along with the symposium, we further celebrate the biology of phagocytes in this issue with a special Review Focus. As part of this Focus, we present three Reviews exploring the cell biological understanding of phagocytosis. Sergio Grinstein and colleagues discuss biophysical aspects of phagocytosis, including the way components of the glycocalyx (the outer covering surrounding many cells) affect the interactions between target cells and phagocytes, and how the mobility of proteins within the membrane affects phagocytosis. Michael Elliott and Kodi Ravichandran review apoptotic cell clearance by phagocytes—a process known as efferocytosis—with a focus on how phagocytes and apoptotic cells find each other and how phagocytes distinguish between dying and living cells. Finally, Anna Huttenlocher and colleagues consider the cell biological basis of neutrophil migration, highlighting in particular the role of the uropod in directing cell movement.Several short pieces complete the Focus by concentrating on specific phagocytic cells and model systems. A Commentary from Katrin Kierdorf and Marc Dionne focuses on macrophages, describing how different environmental and perhaps also developmental factors contribute to a diversity of macrophage activation states. Microglia are the focus of another Commentary, in which Soyon Hong and Beth Stevens describe how these specialized macrophages not only function as immune cells of the central nervous system, but also contribute to brain patterning by pruning synaptic connections. Reflecting on how we came to learn about these and other facets of phagocyte biology, two additional Commentaries highlight the specific contributions of fly and fish studies, where genetic and imaging approaches have enabled unique insights. Helen Weavers and Will Wood comment on the similarities between fly and vertebrate macrophages and the lessons learned from fly macrophages about host-pathogen interactions and the response to injury. Last but not least, Cong Huang and Philipp Niethammer illustrate how imaging studies in zebrafish have provided insight into leukocyte reverse migration, the regulatory role of H2O2, and the interactions between macrophages and mycobacteria.Together, these pieces provide a glimpse into the fascinating and diverse life of phagocytes. We hope you enjoy reading these pieces as much as we have!The Developmental Cell editorial team