Memory isn’t stored in a single place or a single cell—it’s embedded in subtle, widely distributed changes at synapses. In this episode, we explore how neuroscientists moved from abstract theories of memory to concrete biological mechanisms. We follow the trail from Hebb’s insight about synaptic modification to Eric Kandel’s landmark experiments in the sea snail Aplysia, where learning could be traced to specific molecular changes at identifiable synapses. We then bridge simple nervous systems to the mammalian brain, examining how activity-dependent synaptic plasticity links development, learning, and memory. The result is a unifying view of memory as a physical process—measurable, modifiable, and deeply rooted in neural circuitry.