Light is the governor of the universe and hormones. The visible and the invisible forms of light are the parameters which are driving the universe. As we know that all living creatures are already a part of this universe and hence our existence is with light. Light is to be used and not to be abused. Have you ever thought about how much hunger we have for light every day, every hour, when, what type, where, how and why? Why and how light (Natural or artificial) can be used as a medicine? Why be very careful while choosing lights for your homes, offices, schools & healthcare facilities?  The basic fundamentals of human molecular mechanisms and sleep with respect to light are shared through this book. I vow that it will be of some source of knowledge and information triggering your inquisitiveness.