Over our lifetimes we experience multiple viral infections. Some infections are similar to ones we have fought earlier. In the best-case scenario of secondary infection, our pre-existing immunity will jumpstart and neutralize the new, but related, virus. Tulika Singh wants to uncover the immune pathways that remember and reactivate such broadly neutralizing antibodies. She is pioneering tools to measure the parts of our immune response that encompass diversity towards multiple viruses. Singh hopes this work will improve vaccine design to protect the world from emerging viruses.