What state of matter is Jell-O?

Jell-O is a solid that is suspended in a liquid, as it is the product of gelatin and water. This occurs when the solution cools following heating and the proteins bind back together, subsequently forming a matrix and trapping the water molecules. Jell-O is an example of a colloid.

Colloids occur when a substance is microscopically and evenly distributed throughout a second substance. Colloids are one of three types of mixtures; the other two are solutions and suspensions. The particles within a colloid range between 1 and 1,000 nanometers in diameter. Due to the even dispersal of particles, the solid components of the colloid do not settle at the bottom.