Oh I'm so glad you posted this. I've been researching many sites for sensory tables (for indoor use) and while I understand the educational and fun value...but imagining my busy 2 year-olds and rice, sand or water everywhere *shivers*. Love the idea of using the rubbermaid underbed storage boxes...easy to bring out/plan ahead and cover and remove. And some great ideas for materials other than sand, water and rice