The words finance, credit, savings and investments call to mind the world of big business and banking activities on a very large scale. That these financial circuits could somehow be miniaturised gave rise to the term of microfinance, which was coined to describe the way for people to have access to facilities for credit savings and investment on a very small scale. Nowadays, the populations living in rural and peri-urban areas of developing countries participate with their own financial contributions in the development of projects related to water resources supply and sanitation. Local communities also have to contribute to the management of the necessary equipment. But because this kind of equipment is often of small size and cannot be covered by big external financing programmes, these people have had to find ways to create microcredit systems based on solidarity networks.