This article describes fundamental properties of the brain as an organ specialized in signal processing. The emphasis is on neuroanatomy (e.g. fibrousness, geometry of neurons, grey and white matter, different kinds of grey matter, aspects of connectivity, brain size), but built into the context of brain function. Written in an almost poetically condensed style the article allows the reader to grasp essential things at a glance, such as the necessity for ramified cells in the nervous system or the role of different kinds of architecture within the brain. It is a pleasure to read this article and I would not like to change a single line.