What’s the harm in putting a Styrofoam container in the microwave? Styrofoam, which is made of expanded polystyrene, is primarily derived from a chemical called a styrene monomer, or simply styrene. Although it has long been used to make a wide variety of commercial products, it’s not completely harmless to humans. When food is stored in a Styrofoam container, small quantities can be transferred to food. Microwaving speeds up that process. Rolf Halden, a professor in the School of Sustainable Engineering and the Built Environment, part of the Fulton Schools, explains that the heat can generate more free chemical building blocks, and also accelerate the movement of chemicals out of the plastic and into food.