Many useful manmade systems in this world are extremely complex; a typical example is a large infrastructure. No design team ever invents these artefacts because they are too complex. The artefacts are made by combining existing elements (legacy) and by building new subsystems without explicit and comprehensive up-front coordination. To a large extent, these complex systems emerge and evolve. Experience shows that designers often fail to develop artefacts that, when combined, facilitate the emergence of effective and efficient emerging systems. This paper formally elaborates the mechanism behind this phenomenon, and proposes design principles for the design of emergent systems’ components. These principles are discussed and shortly illustrated.