From liquid to solid

When a gelatin solution is hot, the proteins molecules are in constant, forceful movement. As the solution cools, the molecules move more gently. The proteins form regions with helical association, i.e. they coil. A meshwork of gelatin molecules begins to form as these regions bind and align themselves. Liquid becomes trapped in the interstices of the meshwork, preventing a noticeable flow. The liquid becomes a solid gel.