Planets & Moons is a type of group brainstorm that can be used with very large groups. Also, it allows for both idea generation and later qualification and organization of the generated ideas.
_Lots of thick markers
_Lots of sheets of paper
The overall process is (at least somewhat) analogous to Big Bang, hence the name. First the group is asked to produce a lot of moons (ideas). Second, the moons are spread out in space. Third, the group organizes the moons in different groups to form planets (concepts). Fourth, the group forms smaller teams based on interest. They pick a planet to be on. Each team is asked to go through the stack of moons on their planet and use the ideas to create a more qualified overall concept. Finally these concepts are presented to the entire group.
The elaborate diagram below provides a visual explanation.
Group of participants organizing moons in a recent workshop