This chapter explores the motives and opportunities in the Middle Ages for observing and discussing natural things to characterize the ways in which that natural knowledge expressed itself. It focuses on the treatment of beasts, stones, and herbs in medieval scientific writings. The chapter also examines mystic's visions, a schoolchild's Latin assignment, a theologian's dating of Creation, or a sculptor's carving of oak leaves which can tell about the extent of medieval knowledge of natural things. Herbals, bestiaries, and lapidaries were abridged and combined with a strong dash of magic, astrology, and marvels of the world to create the extremely popular genre known as books of secrets and often attributed to Albertus Magnus. The chapter considers the role of visual images in medieval natural history. Several different traditions of illustrating the objects of the natural world ran alongside the written and oral traditions of medieval natural history.