The role of talk in developing understanding in science has been well documented and the recognition of this in the new National Curriculum for England is very positive. The curriculum outlines the need for quality and variety of language in order for children to develop their scientific vocabulary and to articulate scientific concepts clearly and precisely. "I can explain!" is a project that has created training materials and resources to support children with explaining their ideas in science. Using high-quality picture cards and language prompts to facilitate rational discussion, children work in small groups to explore scientific concepts. They develop skills to learn effectively through group talk, and using these they make cognitive gains in science. They learn to justify their scientific ideas with evidence and to counter the ideas of others. The challenge of having to reach a group agreement enables the children to recognise the value of critical consideration of the reasons and evidence they give for their ideas. Funded by the Primary Science Teaching Trust, the resource is now being disseminated to schools across the United Kingdom and can be used flexibly with all ages from nursery to year 6 (ages 5-11). In this article, the author describes the methods used in the project to develop scientific literacy.