Cosmology deals with the current state of thinking about the basic questions at the center of the field of cosmology. More emphasis than usual is put on the connections to related domains of science, such as geometry, relativity, thermodynamics, particle physics, and - in particular - on the intrinsic connections between the different topics. The chapters are illustrated with many figures that are as exact as currently possible, e.g. in the case of geometry and relativity. Readers acquire a graduate-level knowledge of cosmology as it is required to understand the cosmological impact of their particular research topics, as well as an introduction into the current research in the field.