When Professor Karl Deisseroth was studying medicine in the 1990s, he took a rotation working with psychiatric patients.

It would start him down a path of discovery about how the brain works that would eventually lead him to this year’s Nobel Prize in Physiology or Medicine.

He is a pioneer in the field of optogenetics, the ability to control nerve cells with light to investigate how their activity shapes our feelings and behaviour. The hope is that it will allow us to better understand disorders of the brain.

“The brain is billions of fragile, extremely vulnerable, transparent, very fast-acting cells. It’s a very challenging system to study and, of course, buried within the skull and doing very complex things,” he says.