Spectacular eruptions - that's what every child wants out of a science toy, and that is what this delivers. To comfort parents, the eruption is harmless (soda) , but perhaps messy. This is an induced chemical reaction - Mentos chewy mints react explosively with the carbon dioxide gas dissolved in the soda water, the explosion is directed upwards by the tube. Of course you can use coke or other super-carbonated drinks too - but it makes it VERY messy. (Exactly what kids love....) Popular science. Package is 26 cm x 14 cm.