When her beloved grandmother died, it changed the course of Dr Carina Kern's life, sparking a deep desire to understand why ageing makes us more likely to become frail and die and, ultimately, to stop it. Twenty-five years on, the Cambridge-based company she founded with her sister, ex-lawyer Serena Kern-Libera, believes it has made a breakthrough that could change outcomes for all of us. Unlike some research teams working on the science of ageing, they are not working towards immortality ,