The book consists of several thematically interconnected studies on Empedocles that deal with his natural philosophy and related religious topics. It offers a detailed reconstruction of the Sphairos, which is argued to be a giant organism, that is, a structured body with distinguishable parts. This interpretation is supported by some parallels from earlier thinkers and by the history of reception of the Sphairos in the work of later ancient philosophers. Other chapters explain in detail Empedocles' account of the origin of life, embryology, and other biological topics. These innovative scientific ideas are moreover related to some of Empedocles' non-standard religious views, especially his concept of the transmigrating souls.