From 1482 to 1499, Leonardo da Vinci served as a court artisan to Ludovico Sforza, the Duke of Milan. During his time in Milan, da Vinci was able to not only paint and sculpt but also to study a wide variety of other subjects: nature, flying, mechanics, anatomy, and more. da Vinci reportedly hiked in the nearby Alps and often explored various caves where he studied fossils and rock formations. One day, a group of peasants brought da Vinci (who was known for his interest in rocks) a sack of “seashells” they had found in the mountains, further proof of da Vinci’s developing theories on geology.