Platelets have been shown to be associated with pathophysiological processes beyond thrombosis, demonstrating critical additional roles in homeostatic processes, such as immune regulation and vascular remodeling. Platelets themselves can have multiple functional states and can communicate with and regulate other cells, including immune cells and vascular smooth muscle cells, to serve such diverse functions. Although traditional platelet functional assays are informative and reliable, they are limited in their ability to unravel platelet phenotypic heterogeneity and interactions. Developments in methods such as electron microscopy, flow cytometry, mass spectrometry and ‘omics’ studies have led to new insights. In this Review, we focus on advances in platelet biology and function, with an emphasis on current and promising methodologies. We also discuss technical and biological challenges in platelet investigations. Using coronavirus disease 2019 (COVID-19) as an example, we further describe the translational relevance of these approaches and the possible ‘bench-to-bedside’ utility in patient diagnosis and care.