The professor in my class had used this method during our discussion. I think it works when you have several subtopics under a big topic. If you have 4 subtopics, then you'll have 4 expert groups. So if you have 24 students in class, with four topics to study, then you would have 6 home groups: A, B, C, D, E, F, and 4 expert groups: group 1, 2, 3, 4. Each person in their home group is assigned with a topic and then join then expert group to study about the topic. So expert group 1 would include