Capsules are often used as mobile delivery vehicles, for example, in pharmacy, food, and cosmetics, or as stationary containers that are embedded in a matrix to functionalize materials. Progress achieved in polymer chemistry opened up new possibilities to tune the properties of capsules with a much higher precision, thereby allowing the fabrication of advanced materials. This viewpoint summarizes recent developments in the design of functional capsules and highlights some of the challenges involved in the use of capsules to functionalize existing and to build new materials.