Photomicrographs of human lung tissue taken from a patient who died of COVID-19. These are examples of the Neutrophil Extracellular Trap (NET) structures associated with small blood clots. Small blood vessels are outlined with yellow dotted lines, and NETs are identified by the presence of neutrophils (in gray), altered DNA-associated proteins (green). Platelets in the blood clots are in red. Blue color stains DNA in all cells.