This review provides a comprehensive overview of the structure and function of mammalian nicotinic acetylcholine receptors (nAChRs). The discovery of nAChRs began with Langley's classical studies in the early 20th century, which introduced the concept of a "receptive substance." Subsequent research, particularly using the *Torpedo* electric organ and α-bungarotoxin, led to the detailed characterization of muscle nAChRs. The existence of nAChRs in the mammalian brain was confirmed in the late 1980s, and it was found that various nAChR subtypes contribute to the psychoactive properties of nicotine and other drugs of abuse, as well as to the neuropathology of diseases such as Alzheimer's, Parkinson's, and schizophrenia. nAChRs consist of two major subtypes: metabotropic muscarinic receptors and ionotropic nicotinic receptors. The muscle nAChR is a heteropentamer composed of four related but distinct subunits, organized around a central pore. The discovery of α-bungarotoxin, which binds to muscle nAChRs with near-covalent affinity, facilitated the purification and cloning of nAChR subunits. The diverse functions of nAChRs are regulated by their subunit composition, which determines their pharmacology and specific roles in physiological processes. The review also discusses the antiquity of nAChRs and their coevolution with predators and prey. Nicotine, produced by plants as a defense mechanism, is a potent nAChR agonist that has been widely used for its therapeutic and recreational effects. Various toxins, including α-bungarotoxin and conotoxins, target nAChRs and are used in both predatory and defensive strategies. Finally, the review explores the transcriptional regulation and assembly of nAChR subunits, highlighting the importance of gene duplication and coordinated expression in maintaining the diversity and function of nAChRs.This review provides a comprehensive overview of the structure and function of mammalian nicotinic acetylcholine receptors (nAChRs). The discovery of nAChRs began with Langley's classical studies in the early 20th century, which introduced the concept of a "receptive substance." Subsequent research, particularly using the *Torpedo* electric organ and α-bungarotoxin, led to the detailed characterization of muscle nAChRs. The existence of nAChRs in the mammalian brain was confirmed in the late 1980s, and it was found that various nAChR subtypes contribute to the psychoactive properties of nicotine and other drugs of abuse, as well as to the neuropathology of diseases such as Alzheimer's, Parkinson's, and schizophrenia. nAChRs consist of two major subtypes: metabotropic muscarinic receptors and ionotropic nicotinic receptors. The muscle nAChR is a heteropentamer composed of four related but distinct subunits, organized around a central pore. The discovery of α-bungarotoxin, which binds to muscle nAChRs with near-covalent affinity, facilitated the purification and cloning of nAChR subunits. The diverse functions of nAChRs are regulated by their subunit composition, which determines their pharmacology and specific roles in physiological processes. The review also discusses the antiquity of nAChRs and their coevolution with predators and prey. Nicotine, produced by plants as a defense mechanism, is a potent nAChR agonist that has been widely used for its therapeutic and recreational effects. Various toxins, including α-bungarotoxin and conotoxins, target nAChRs and are used in both predatory and defensive strategies. Finally, the review explores the transcriptional regulation and assembly of nAChR subunits, highlighting the importance of gene duplication and coordinated expression in maintaining the diversity and function of nAChRs.