This brings back fond memories of childhood. I adored Sunprint Kits when I was a kid and I am so happy that they are still around (it's been since 1975!). You remember how they work? You lay objects onto of the blue sheets and place them in direct sunlight. The areas of the paper exposed to light turn white while the blue molecules in the paper remain under the object, creating a perfect silhouette. Rinse them in water and watch the white turn to blue and the blue to white. Basically.... it's science.