Within the depth-psychology and neuroscience corpus assembled under the Seba library, ‘nucleus’ operates across several registers that intersect but rarely collapse into one another. At its most elementary, the term designates the cellular organelle housing the genome — the commanding interior of the neuron from which protein synthesis is orchestrated and, crucially, from which long-term memory consolidation is initiated. Kandel’s molecular-biological program makes the nucleus the decisive gateway through which repeated learning trials are translated into stable synaptic growth: signals must reach the nucleus to activate regulatory genes, and blocking this process arrests the conversion from short- to long-term memory. Damasio extends the cellular framing philosophically, treating the nucleus-cytoplasm dyad as the primordial site of homeostatic ‘will’ — a proto-intentionality that precedes consciousness itself. In neuroanatomical usage, ‘nucleus’ also designates discrete brainstem and forebrain structures whose functions are pivotal to affect regulation and autonomic control: the nucleus ambiguus (Porges), the nucleus accumbens (Koob), the paraventricular nucleus, the nucleus of the solitary tract, and the nucleus tractus solitarii all figure prominently. Porges, in particular, treats nucleus ambiguus function as the neurophysiological index of the neomammalian vagal brake and the proximate substrate of social engagement. Koob situates the nucleus accumbens at the center of addiction neurocircuitry. The term thus bridges molecular biology, autonomic neurophysiology, and affective neuroscience, functioning as a site of mechanistic precision across otherwise divergent theoretical projects.