Bacteriophage Phi-6, which serves as a model system for rotavirus, is the most common cause of diarrheal disease in infants and young children. An understanding of how bacteriophage assemble can help scientists develop new ways to treat rotavirus infections. Shown here is a cryo-electron microscopy image of the protein shell of Phi-6, or procapsid, opened to show the different protein types: P1 (blue), P4 (red), P7, yellow, and P2 (purple).