Bacterial cells have an added layer of protection, called the cell wall, that animal cells don’t. Assembling this tough armor entails multiple steps, some of which are targeted by antibiotics like penicillin and vancomycin. Now researchers have provided the first close-up glimpse of a protein, called MurJ, which is crucial for building the bacterial cell wall and protecting it from outside attack. The findings could be used to develop new broad-spectrum antibiotics.