What is the story behind the creation of the novel Frankenstein?

Shelley travelled through Europe in 1814, journeying along the River Rhine in Germany with a stop in Gernsheimwhich is just 17 km (10 mi) away from Frankenstein Castle, where, two centuries before, an alchemist was engaged in experiments. Later, she travelled in the region of Geneva and the topic of galvanism and other similar occult ideas were themes of conversation among her companions, particularly her lover and future husband, Percy Shelley. Mary, Percy, Lord Byron and John Polidori decided to have a competition to see who could write the best horror story. After thinking for days, Shelley dreamt about a scientist who created life and was horrified by what he had made; her dream later evolved into the novel's story.