In 1897, German chemist Adolf Spitteler discovered that milk, when mixed with formaldehyde, turns into a plasticlike material. Check that: His cat made the discovery, Scientific American reports. During a night incursion into the lab, the cat bumped into a bottle of formaldehyde, spilling the contents into its milk bowl. The morning after, Spitteler found that the milk had curdled into a solid material. Curiosity (sadly) killed his cat, but it opened a new, productive avenue of research for Spitteler, who several years later started the first company to make milk plastic—otherwise known as solid casein, the main component of cheese. Casein plastics were widely used, especially for the production of buttons, until the 1930s.