English: Soap bubble consists of water and soap. Due to the forces of surface tension of the bubble takes a spherical shape. The strength of the Earth's gravity acts on the liquid molecules and these molecules are attracted to one another. Molecules on the surface of which are subject to a stronger attraction than the molecules that are outside. A soap bubble is trying to reduce its surface which it covers. The sphere has the smallest area among the bodies of equal volume. Therefore, the bubble takes a spherical shape. The physical process of interference creates a rainbow of colors on the surface of the bubble. The wall thickness of the bubble than the wavelength of visible light several times.