Oooohhhhh I found a great sensory activity! I can't wait to try this with my daughter tonight! We've made slime in the past, mixing equal parts Elmer's glue and liquid starch. A couple of times we've added glow in the dark paint to the mix for something different. This mom and her little girl made rainbow slime using Elmer's clear glue and liquid starch. (follow the link for her exact recipe) Then they separated it out and used food coloring to make 4 colored batches and had fun mixing it all together. I'd bet it would be even more fun on a light box.