The mammalian the olfactory bulb (OB) maintains a continuous inflow of new neurons to its circuitry throughout adulthood. The role of these newborn neurons in sensory processing or the bulbs’ function remains completely unknown. We use in vivo imaging and electrophysiology to study the structure and function of these neurons. I will present our studies of the development and plasticity of adult-born interneurons as well as that of their resident counterparts. Specifically we use two-photon imaging of single neurons to probe their morphology and two-photon targeted patch to study their physiology in high spatiotemporal resolution. I will discuss our data showing that newborn neurons mature to become integral elements of the sensory coding machinery during the very early stages of olfactory processing. Furthermore, we argue that our results challenge some basic dogmas in the field of adult neurogenesis.