T follicular helper cells (Tfh) are essential for strong antibody-mediated reactions of our immune system during infections and vaccinations. However, if they get out of control, this can cause diseases such as autoimmunity, allergies or cancer. Researchers have investigated the underlying mechanisms of Tfh cell development in a mouse model and thus decoded their internal networking. They hope that this will lead to new strategies for the development of highly effective vaccines and new therapies to combat various diseases.