Discovery sessions are usually based around a stimulus that the teacher has set up. When children are all doing something similar, watching what happens, talking about the science that is going on, the teacher has a way in to learn about their understanding, but then the teacher can take it deeper into exploring their skills in working scientifically. Teachers ask the children to think about what questions they have and how they could change the investigation. In this article, the author presents discovery sessions and discusses why assessment is not something that happens in the plenary at the end of a lesson; it starts with planning and should be embedded throughout the teaching.