This case study explores the neurobiological mechanisms and physiological consequences of nicotine addiction, focusing on its impact on the brain, long-term health, and sleep quality. Students read the story of “Sarah,” who develops a nicotine dependency in high school that ultimately leads to a health crisis at age 52. They then analyze Sarah’s medical information to examine the complex molecular interactions of nicotine and their consequences for the body. Students learn that nicotine’s potency stems from its structural similarity to acetylcholine (ACh), enabling it to rapidly bind to and activate nicotinic acetylcholine receptors (nAChRs) in the brain. Although nicotine is often perceived by users as calming, it significantly alters brain function by modulating neurotransmitter systems involved in reward, mood, and cognition. Originally designed for an upper-level biology elective course focusing on the neurobiology of addiction, this case study could also be used in introductory neuroscience courses or in anatomy and physiology courses when learning about the brain.