Loss or reduction of the sense of smell can feel discouraging, particularly because recovery is often slow and unpredictable. Unlike many other sensory systems, olfaction has limited medical treatment options, and for years, patients were told little could be done beyond waiting. Over the past decade, this view has changed. Growing evidence shows that the olfactory system retains a remarkable capacity for adaptation and recovery when it is deliberately and repeatedly stimulated. Smell training has therefore emerged as a cornerstone of modern olfactory rehabilitation. Smell training is simple in principle but powerful in effect. By repeatedly exposing the nose and brain to a small set of odors, the olfactory system can be challenged in ways that promote recovery, reorganization, and improved function. Although progress is often gradual and requires patience, smell training is safe, inexpensive, and accessible to most individuals. Importantly, it empowers patients to actively participate in their own rehabilitation rather than relying solely on medication or surgery. In this chapter, we explain what olfactory training is, how it is performed, and why it works. We review the scientific evidence supporting its use across different causes of smell loss, including post-viral infection, head injury, aging, and idiopathic olfactory dysfunction. The chapter also explores the biological mechanisms behind smell training, from changes in the nasal sensory tissue to structural and functional adaptations in the brain. Finally, we discuss variations of training protocols, practical strategies to improve adherence, and emerging findings suggesting broader cognitive and emotional benefits beyond smell recovery. Together, this chapter provides both the scientific foundation and practical guidance needed to use smell training effectively as part of olfactory rehabilitation.