Acrolein (propenal) is the simplest form of unsaturated aldehyde. Its synthesis from glycerol and some of its typical reactions have been known since 1843. It was observed at that time that the fluid acrolein spontaneously changed upon standing to a white, solid product, suspected to be a polymer. Acrolein became available on a technical scale in 1942, resulting in intensive research on the suitability of the compound in organic syntheses and polymerizations. Characterization and methods of polymerization are presented.