The article gives, first of all, a general presentation of the European Space Agency (ESA), followed by a more detailed outline of the ESA's Science Programme, its content, resources, organization, advisory structure and decision procedures. The various types of missions and the place they occupy in the programme are described. From a scientific point of view, these missions fit into four main themes of research, which are also potential ‘roadmaps’ for international collaboration. In the second part of the article, an outline is given of most of the projects that have been already undertaken, are in process or are being planned at the present time.