Previous studies have pointed to the benefits of involving students' everyday life experiences in lessons and in contextualizing the science content to enhance learning and positive attitudes toward school science. However, most of these investigations have been conducted as intervention studies. By contrast, the present study explored how teachers, in authentic situations and without interventions, related the school science context to other contexts. We analyzed a total of 490 min of lesson introductions in Swedish Grade 9 classes. The results revealed that teachers employed contextualization at the intersection of science content and the everyday life context, the school context, and the language context. Furthermore, it appeared that contextualization was created in the moment, as a way of explicating the scientific content. Compared to intervention studies, the present study shows that occasions of contextualization are rare. It is possible to conclude that the use of contextualization in science learning situations could be viewed as a teacher competence and must be explicit in teacher education and professional development to achieve the benefits of enhanced student interest and learning shown in the mentioned intervention studies.