Styrofoam is a trademark of The Dow Chemical Company for closed-cell extruded polystyrene foam currently made for thermal insulation and craft applications. In 1941, researchers in Dow’s Chemical Physics Lab found a way to make foamed polystyrene. Polystyrene is a thermoplastic substance, which is in solid (glassy) state at room temperature, but flows if heated above its glass transition temperature (for molding or extrusion), and becomes solid again when cooled. Pure solid polystyrene is a colorless, hard plastic with limited flexibility. Dow also produces Styrofoam as a structural material for use by florists and in craft products. Dow insulation Styrofoam has a distinctive blue color; Styrofoam for craft applications is available in white and green. (Wikipedia)
Styrofoam is one of the versatile materials for making visual merchandising props because of lightness and softness; also because these characteristics, Styrofoam is a safe and easy-to-use material for indoor displays and decoration.