When it comes to fending off disease and helping prevent people from falling ill, the body’s immune system — armed with T-cells that help eliminate cancer cells, virus-infected cells and more — is second to none. But exactly how the immune system works remains, in many ways, a mystery. Now, a team of scientists has developed the Just EGFP Death-Inducing T-cell, or JEDI T-cells, which enable the visualization of T-cell antigens, allowing researchers to study T-cell interactions with different cell types, model disease states, and finally determine the functions of otherwise poorly characterized cell populations.