Design practices and artifacts are ubiquitous. From a scientific-theoretical perspective, the concept of design is gaining increasing importance. It encompasses far more than just the aesthetic enhancement of consumer products. Design theories address the fundamental 'constructedness' of our reality, thereby opening up an interdisciplinary field of research that goes beyond the traditional notions of design as a craft practice. This volume by Claudia Mareis introduces key design theories of the 20th century, starting from the design itself. It outlines approaches and models that propose an expanded concept of design and establish interdisciplinary interfaces with the humanities and engineering sciences, as well as with society.