In 2023, nothing seems more obvious than the fact that doctors should wash their hands in between patients. But this wasn’t always the case. And we owe our knowledge of this “obvious” fact to one of the most famous scientific dissidents in history: Ignaz Semmelweis. In 1846, the Vienna General Hospital had two free obstetric clinics, where underprivileged women, including prostitutes, could go to receive not only child-birthing services, but also free postpartum care for their infants. In return for the free services, the new mothers agreed to be used as subjects for the training of doctors (in the first clinic) and midwives (in the second). But giving birth in the first clinic was extremely dangerous.