Smell is one of the five senses. It is how we interact with the world. What does the smell of a good meal mean to you? What are good smells and what are bad smells? Are there effects beyond just being pleasant or unpleasant? Specific odors that represent food or indicate danger may be capable of altering an animal’s lifespan and physiological profile by activating a small number of highly specialized sensory neurons, researchers at the University of Michigan, University of Houston, and Baylor College of Medicine have shown in a study publishing by the end of April in the online, open-access journal PLoS Biology.