Scientists have developed a smarter way to activate the immune system against cancer, potentially making treatments safer and more precise. When triggered, STING acts like an internal alarm system, sending out signals that summon the body's immune system to attack. Together, the two pieces form a powerful STING activator, switching on the immune system only where the cancer is located. The molecules are designed to recognise and stick to each other efficiently, so the reaction happens quickly and selectively inside tumours. By using a simple chemical design, the Cambridge team achieved targeted activation of the immune system without relying on complex or artificial reactions.