At the end of the day, when humans sink tiredly into their pillows, they close their eyes, plug their ears against noise, and sleep. No such rest is accorded the nose. It works nonstop. Day and night, 24 h, a lifetime. While humans surrender to their dreams, their noses watch over them and continue to sniff. As long as we breathe, we smell. Completely automatic. We can’t turn off the nose, because, after all, you can’t hold your breath for too long. Some scents are particularly pleasing to the nose, such as the scent of oranges or roses. In that case, the human dreams something beautiful. Conversely—as our experiments in sleep labs have shown—stench can have the opposite effect: When faced with the foul smell of feces, people report unpleasant experiences in their dreams upon waking.