This document discusses teaching as a design science. It explains that teaching has traditionally been viewed as an art, but it is also a science with defined goals. Educational research aims to build and improve design principles for teaching based on theoretical sciences and feedback into those sciences. Design sciences are about how the world could or should be. The document outlines how design research is used in initial teacher training and with in-service teachers to develop theories about learning, intervene to understand situations, and iteratively improve teaching through projects and collaboration. It encourages teachers to participate in and share educational design research.