Bubbles

A soap bubble is an extremely thin film of soapy water enclosing air that forms a hollow sphere with an iridescent surface. Soap bubbles usually last for only a few seconds before bursting, either on their own or on contact with another object. They are often used for children's enjoyment, but they are also used in artistic performances.
When light shines onto a bubble it appears to change colour. Unlike those seen in a rainbow, which arise from differential refraction, the colours seen in a soap bubble arise from interference of light reflecting off the front and back surfaces of the thin soap film. Depending on the thickness of the film, different colours interfere constructively and destructively.
17th-century Flemish paintings show children blowing bubbles with clay pipes verifying soap bubbles being used as entertainment for at least 400 years. The London-based firm of A. & F. Pears created a famous advertisement campaign for its soaps in 1886 using a painting by John Everett Millais of a child playing with bubbles.
 A Chicago company called Chemtoy began selling bubble solution in the 1940s, and they have been popular with children ever since. According to one industry estimate, retailers sell around 200 million bottles annually.
[Wikipedia]