The book is dedicated to the medieval “science of sciences” - alchemy. As the author shows, despite the secret nature of the alchemists’ activities and contrary to popular ideas about the renunciation of their activities, adepts used their science as a means of understanding and transforming God’s world, most often remaining within the framework of the orthodox church. The daily lives of the alchemists, their theories, symbols, instruments and laboratories, and contributions to experimental chemistry, art, architecture and literature are vividly recreated by the famous French historian Serge Hutin.