The introduction to global informality will address the very basic of informal production energies. Informal housing solutions and informal economies owe their persistent existence not only to exogene forces, as to say the incapacity of formal provision, but also to its inner strength in flexibility and resource-optimization. Despite the apparent downside of informality towards health and environmental safety, there is much to learn from its creative and effectiveness. Therefore a journey through-out the world will help to illustrate the scope of urban informality and stimulate discussions how to use them for planning and design practices.