In Mary Shelley’s Frankenstein, lightning is a metaphor. In film adaptations, it’s famously also a direct mechanism. It is the flash that splits the sky, the force that animates the creature, and the reminder of how close life and death can sit to one another. But the heart is its very own electrical organ. Each beat begins with a spark; not from the heavens, but from the sinoatrial (SA) node, a cluster of cells in the right atrium. These cells spontaneously depolarize, setting off an electrical

A jolt of lightning bringing Frankenstein's monster to life wasn't purely Shelley's invention. It was inspired by an 18th century scientific movement known as "galvanism." | Vox