Enveloped viruses gain entry to mammalian cells by interaction of trimeric envelope glycoproteins (“entry spikes”) with cellular receptors. Understanding the structure and structural changes of these “entry spike” complexes is important for understanding entry mechanisms and for the design of effective vaccines. We have developed powerful tools for determination of entry spike structures that enabled us to obtain the first 3D structures of HIV-1 envelope glycoproteins in their native states and in complex with a variety of neutralizing antibodies. Our current work is focused on understanding the structural biology of coronaviruses, in particular SARS-CoV-2, the causative agent of COVID-19.