The complexity of the brain's structure and chemical composition, that somehow this complexity creates a new category of functional properties. This complexity enables us to think and dream, calculate and talk, see and draw. But again, these are basic tasks that most animals can handle too. What we are most in awe of about our selves as humans, and this is how we would like to distinguish us from animals, is our ability to think, exercise free will, accept morality, and to be creative. Every scientific expert in consciousness research has his or her own favorite explanation.
Theories are abundant, experimental evidence scarce.
Sleep is undoubtedly one of the most important factors structuring our lives. The necessity for animals to sleep, and the concomitant problems associated with a lack of sleep have a tremendous effect on our ability to function on a daily basis. While the role of sleep as part of the physiology of our body is entirely elusive, the results of the lack of sleep are well documented. The question of how sleep works at the molecular level is subject to a tremendous effort in basic research. These are the same structures identified in various brain functions for cognition, motor control, speech, memory and consciousness.