By now you know that circadian clocks organize our daily biology and physiology. This is true for practically all organisms and even for many processes within the cell. The oscillator, the mechanism that generates the circadian rhythmicity, is only meaningful if it conveys its internal timing to the rest of the organism or the cell. These hands of the clock are also called the circadian outputs. That systematically affect our metabolism and behaviour. In this lecture, Martha will show you many examples of clock outputs from humans to, surprisingly, bees. To better understand the results, she will explain the special experimental protocols that are used to study human circadian rhythms. Then she will discuss the different levels of clock regulation from a dedicated area in the brain to clock genes in the cells. Finally, several examples of genetic regulation should give you an idea of how the circadian clock regulates personality and mood, as well as major physiological processes. Understanding clock regulation will help you appreciate what the clock actually does. It will also be important for the understanding of the significance of the clock in health and illness.