Industrial ecology? A surprising, intriguing expression that immediately draws our attention. The spontaneous reaction is that "industrial ecology" is a contradiction in terms, something of an oxymoron, like "obscure clarity" or "burning ice". Why this reflex? Probably because we are accustomed to considering the industrial system as isolated from the Biosphere, with factories and cities on one side and nature on the other, as well as the recurrent problem of trying to minimise th impact of the industrial system on what is "beyond" it: its surroundings, the "environment". As early as the 1950's, this end-of-pipe angle was the one adopted by ecologists, whose first serious studies focused on the consequences of the various forms of pollution on nature. In this perspective on the industrial system, human industrial activity as such remained outside the field of research. Industrial ecology explores the opposite assumption: The industrial system can be seen as a certain kind of ecosystem. After all, the industrial system, just as natural ecosystems, can be described as a particular distribution of materials, energy, and information flows. Furthermore, the entire industrial system relies on resources and services provided by the Biosphere, from which it cannot be dissociated. (It should be specified that "industrial", in the context of industrial ecology, refers to all human activities occurring within modern technological society. Thus, tourism, housing, medical services, transportation, agriculture, etc. are part of the industrial system.) Besides its rigorous scientific conceptual framework (scientific ecology), industrial ecology can also be seen as a practical approach to sustainability. It is an attempt to address the question, "How can the concept of sustainable development be made operational in an economically feasible way?" Industrial ecology represents precisely one of the paths that could provide concrete solutions. Governments have traditionally approached development and environmental issues in a fragmented and compartmentalised way. This is illustrated in the classical end-of-pipe strategy for the treatment of pollution, which has proven to be quite useful, but not adequate to make an efficient use of limited resources, in the context of a growing population with increasing economic aspirations. Thus, industrial ecology emerges at a time when it is becoming increasingly clear that the traditional pollution treatment approach (end-of-pipe) is not only insufficient to solve environmental problems, but also too costly in the long run.