Why did Mary Shelley write Frankenstein?

Mary Shelley wrote "Frankenstein" as a result of both her interest in scientific theories of the time and as part of a challenge to write a ghost story. In 1816, Mary Shelley, her husband Percy Bysshe Shelley, Lord Byron, and John Polidori gathered at Villa Diodati by Lake Geneva. The year was marked by a volcanic winter caused by the eruption of Mount Tambora in 1815, leading to what was known as the Year Without a Summer. Because of the inclement weather, the group ended up spending a lot of time indoors, and Lord Byron proposed that everyone should write a ghost story.

Mary Shelley, inspired by the conversations about life and the principles of existence that were common between her husband and Byron and influenced by the scientific discussions of the time, particularly those concerning galvanism and the possibility of reanimating the dead, conceived the idea of "Frankenstein." After a vivid dream about a scientist who gives life to a creature, she began to write her story, which would become one of the most famous horror novels of all time.

"Frankenstein; or, The Modern Prometheus" was published in 1818 when Mary Shelley was only twenty years old. In addition to the challenge and the scientific trends of the period, the novel also reflects Mary Shelley's thoughts on various themes including the dangers of playing God, the ethics of scientific experimentation, isolation, and the nature of humanity.