Gelatin is made of long strings of proteins known as polymers released from the collagen in the skin, bones and connective tissue of animals as it is broken down by heat and water. Dissolved in water and cooled, it forms a “gel”, a word first coined by the 19th-century Scottish chemist Thomas Graham, through shortening “gelatin”. A gel has the density and weight of a liquid, but acts like a solid because of the internal cross-linking of polymer chains. That’s why jellies wobble – tap one and the energy passes through it like ripples across a liquid. As soon as heat is applied, these cross-linkings untangle themselves, the surface tension breaks, and the gel returns to its liquid state.