Fun became earnest. Others play with them as children, Frank Huster - architect, designer and lecturer - turns them into his life's mission. Toys and houses out of paper and corrugated cardboard mark the start of a development that culminated in pre-fabricated building systems made from steel and plastic. Ultimately, this developed into his speciality: pre-fabricated wet rooms, sometimes as modular component systems. Architecturally clever, scientifically based.