In August 2003 over 400 researchers in the field of science education from all over the world met at the 4th ESERA conference in Noordwijkerhout, The Netherlands. During the conference 300 papers about actual issues in the field, such as the learning of scientific concepts and skills, scientific literacy, informal science learning, science teacher education, modeling in science education were presented.The book contains 40 of the most outstanding papers presented during the conference. These papers reflect the quality and variety of the conference and represent the state of the art in the field of research in science education.