The morphological development of polyoxymethylene crystals polymerized from and grown within trioxane crystals was observed following irradiation of the trioxane with alpha particles and a subsequent heat treatment. A novel method of sample preparation enabled the morphology to be observed in detail and resulted in the discovery of new forms of polyoxymethylene crystals as well as an improved description of previously reported forms. A solid‐gas‐solid crystal growth mechanism was postulated to account for the predominantly acicular habit of the polyoxymethylene crystals.