Literally translated, sema tawy means "the union of the two lands" of upper and lower Egypt, but the hieroglyphic sign for this union is derived from the lung and trachea and also means "to breathe". The book explores the mythic background of this fundamental polarity and its textual and graphic expressions. Breathing is definitely the essential prerequisite of human and animate life. Perceiving Egypt as a living Being, as the ancient Egyptians used to do, its life depended on its breath, the multi-layered rhythmical respiratory process whose outward appearance was seen in the river Nile and whose hidden implications permeated every part of Egyptian culture. Sema tawy is one of the fundamental concepts of ancient Egypt. A multitude of sema tawy symbols adorn the thrones of the Egyptian kings and the walls of temples and tombs. In spite of their omnipresence they do not belong to the favorite topics of egyptologists, and tourists have never paid much attention to them.