Why are cells so small? Why aren't cells larger? Wouldn't it be more efficient to have larger cells? When your students cut open their stained agar cells and see the diffusion pattern for themselves, the answers will be obvious. Student measurements and calculations during this hands-on laboratory will dramatically clarify the concept of surface area to volume ratio. This concept is key to understanding cell size limitations. Teacher Notes, reproducible student handouts, and all necessary chemicals and specialized equipment are provided. Complete for 30 students working in pairs. Super Value Kit is complete for 5 classes of 30 students working in pairs.