In recent decades, the advent of electric light has seen a paradigm shift in human behaviour. We have moved from spending 90% of our waking hours outdoors to now 90% of this time indoors under artificial light. However, for tens of thousands of years, people have evolved in harmony with the Earth’s natural lighting cycle, adapting our activities across the day in line with the changing conditions of the sun. These varying lighting conditions have always been at the very heart of a human being’s 24-hour internal clock, with a direct link to our productivity, sleep patterns, mood and even physical wellbeing. What are the consequences of our move to the indoors and how can we best light our spaces to deal with this change in the way that we live?