What is consciousness? In a simple sense it may be thought of as awareness, however modern definitions suggest a far greater complexity. In this lecture, we will begin by defining consciousness (a difficult task in itself) and then consider when it develops in the animal kingdom. Is a worm conscious? A bat, a dog, a dolphin? How complex does a nervous system need to be for consciousness to arise? Can consciousness arise from the electrochemical and biophysical processes within small circuits of nerve cells or does an animal require a brain? Is a human foetus conscious? If so, when during prenatal development does it emerge? If not, what kinds of postnatal brain activity and structure are associated with its emergence? What happens to consciousness when the brain is damaged and what can learn about it from studying patients undergoing general anaesthesia or in coma states? This is a lecture intended to make you think about the very nature of being human (and, non-human)!