Diversity in habitats on Earth is astounding--whether on land or in the sea--and this is in part due to symbiosis. The lesson described in this article helps students understand how symbiosis affects different organisms through a fun and engaging game where they match hosts and symbionts based on their respective needs. This 45-minute lesson is most successful when it follows a lesson on foodwebs, in which students learn how different organisms are connected. (Contains 1 figure and 3 online resources.)