Abstract: The invention provides systems and methods for monitoring the sleep of a user and modulating a user's circadian rhythm. A monitoring device is provided for monitoring the sleep behaviour and environment of a user and a lighting device is provided for modulating the circadian rhythm of a user. In embodiments, the systems and devices comprise a motion sensor, environmental sensors and LEDs. The data 10 collected by the monitoring device allows a user's circadian rhythm to be modelled and a lighting schedule to be determined and received by the lighting device for modulating the circadian rhythm.