At school today, the kids were doing a science experiment, which had them all oohing and aahing.
Milk in a plate, with drops of 4 different food colouring. Dip a cotton bud in detergent, then place in the middle of the plate. The food colouring miraculously begins to mix and make wonderful patterns.
@julzmaioro I think the one you are thinking of is when you blow bubbles in a glass of coloured water and then put paper over the top, giving a great bubble print.
Great collage!