The fact that organisms spend about a third of their time in sleep, and that sleep deprivation can have disastrous effects ultimately leading to death demonstrate the importance of sleep. The development of improved imaging techniques like EEG, PET and fMRI, along with high computational power have led to an increasingly greater understanding of the mechanisms underlying sleep.

Starting point is Wikipedia entry, November 3, 2014 and Wikipedia entries for Sleep and the Insomnia Hub.