Microworld (scaled world) simulations are computer based experimental systems for studies on distributed decision-making and team work in dynamic environments. Microworlds have been used in various studies since the late 70ís. They are sometimes seen as bridging the gap between laboratory studies and field research. Microworlds create small, low-fidelity and well-controlled simulation environments. The designer can select important characteristics of the real system and create a simulation system with these characteristics. The simulations are characterized as complex, dynamic and opaque. Present microworlds can be almost as complex as reality itself. Microworlds are suitable for investigating how people behave when they are confronted with a dynamic problem. They are also suitable for investigating the effects of information and communication technologies in relation to the ability to handle dynamic problems.