Invention of the terrarium as we know it is credited to Dr. N. B. Ward of London. Ward was interested in growing many types of ferns in his backyard but had not been successful. While studying a sphinx moth emerging from the chrysalis he had buried in moist earth in a closed bottle, he was amazed to see a seedling fern and some grass growing inside. He watched them grow for four years, during which time not one drop of water was added, nor was the cover removed.
Ward continued his observations with other plants in containers, and in 1842 published a book called On the Growth of Plants in Closely Glazed Cases. This led to development of "Wardian Cases," which were large, enclosed containers for growing delicate plants in the home or transporting precious plants over long distances. The terrariums most often used today are small ornamental versions of the Wardian case.