<p>Lipid droplets (LDs) are emerging as key factors in cellular physiology, with roles beyond energy storage, including metabolic homeostasis, signalling and development. Together with a growing list of functions, diverse LD populations are being identified in different tissue types as well as within the context of single cells. Here we summarize recent work highlighting LD diversity from three perspectives: their lipid and protein compositional heterogeneity; differences in abundance, size and spatial organization within cells; and the diverse contacts they form with other organelles, all of which contribute to LD function. We also discuss tools and approaches used to visualize LD heterogeneity, the role of LDs in pathophysiology and disease, and open questions in the field.</p>