In this lesson, students will learn about the complexity and organization of multicellular animals through the process of regeneration/healing. Planarian flatworms are able to regrow almost every part of their body after injury (a full worm can be formed from tiny pieces), and in order to do this they must re-establish biological organization for their new body parts. The proper cell types need to be produced, those cells must arrange into functional tissues, the tissues then form discrete organs, the organs arrange into organ systems, and finally the organ systems form the proper interconnections. Students will learn these concepts through presentation, activities, and follow up assessment.