At Harvard University, a group of creative scientists have turned the brains of mice into beautiful tangles of colour. By mixing together a palette of fluorescent proteins, they have painted individual neurons with up to 90 different colours. Their technique, dubbed ‘Brainbow’, gives them an unprecedented vision of how the brain’s cells are connected to each other.

The art of looking at neurons had much greyer beginnings. Over a century ago, a Spanish scientist called , one of the founders of modern neuroscience, became the first person to get a clear look at the neural network that houses our thoughts. He found that neurons stood out among other cells when stained with a silver chromate salt.

These monochrome