In this review, we discuss some of the neural processes involved in the perception of odors that, together with audition and vision, provide essential information for analyzing our surroundings. We shall see how odor detection and learning induce substantial structural and functional changes at the first relay of the olfactory system, i.e., the main olfactory bulb. Among the mechanisms that participate in these modifications is the persistence of a high level of interneuron neurogenesis within the adult olfactory bulb. Our goal is to present some observations related to the neurogenesis that may aid in understanding the neural mechanisms of sensory perception and shed light on the cellular basis of olfactory learning. We summarize the current ideas concerning the molecular mechanisms and organizational strategies used by the olfactory system to transduce, encode, and process information at various levels in the olfactory sensory pathway. Due to space constraints, this review focuses exclusively on the olfactory systems of vertebrates and primarily those of mammals.