Breathing is a vital behavior that is particularly amenable to experimental investigation. This review discusses three key aspects of breathing: (i) the generation of respiratory rhythm, (ii) the plasticity necessary for adaptive changes in breathing, and (iii) the sensing and processing of breathing-regulated variables such as CO₂ and pH. The preBötzinger Complex (preBötC) is a critical site for generating respiratory rhythm, and recent studies suggest that coupled oscillators may be involved. Serotonin-dependent long-term facilitation following intermittent hypoxia is an important example of respiratory plasticity, and a model that can account for this adaptive behavior is discussed. Neurons with appropriate chemosensitivity are spread throughout the brainstem; their individual properties and collective role are just beginning to be understood. Central chemoreceptors, which are essential for appropriate breathing in relation to metabolism, are located in the brainstem and are involved in sensing CO₂ and pH. The neural circuits underlying breathing must be stable yet responsive to changes in O₂, CO₂, and pH levels. Breathing is also a special behavior from an experimental perspective because its systems-level activity is present in reduced vertebrate preparations, even in vitro. The review highlights recent progress in understanding the mechanisms of breathing, including the role of the preBötC in rhythm generation, the involvement of serotonin in respiratory plasticity, and the distribution and function of central chemoreceptors. The study of breathing provides insights into the neural mechanisms underlying respiratory control and has implications for understanding respiratory disorders, including Sudden Infant Death Syndrome (SIDS).Breathing is a vital behavior that is particularly amenable to experimental investigation. This review discusses three key aspects of breathing: (i) the generation of respiratory rhythm, (ii) the plasticity necessary for adaptive changes in breathing, and (iii) the sensing and processing of breathing-regulated variables such as CO₂ and pH. The preBötzinger Complex (preBötC) is a critical site for generating respiratory rhythm, and recent studies suggest that coupled oscillators may be involved. Serotonin-dependent long-term facilitation following intermittent hypoxia is an important example of respiratory plasticity, and a model that can account for this adaptive behavior is discussed. Neurons with appropriate chemosensitivity are spread throughout the brainstem; their individual properties and collective role are just beginning to be understood. Central chemoreceptors, which are essential for appropriate breathing in relation to metabolism, are located in the brainstem and are involved in sensing CO₂ and pH. The neural circuits underlying breathing must be stable yet responsive to changes in O₂, CO₂, and pH levels. Breathing is also a special behavior from an experimental perspective because its systems-level activity is present in reduced vertebrate preparations, even in vitro. The review highlights recent progress in understanding the mechanisms of breathing, including the role of the preBötC in rhythm generation, the involvement of serotonin in respiratory plasticity, and the distribution and function of central chemoreceptors. The study of breathing provides insights into the neural mechanisms underlying respiratory control and has implications for understanding respiratory disorders, including Sudden Infant Death Syndrome (SIDS).