Crystal polymorphism, the existence of different crystal structures for the same chemical compound, is a common phenomenon in chemistry. Many compounds are known to form multiple polymorphs depending on the crystallization conditions. Different polymorphs can have different physical and chemical properties, such as density, melting point, hardness, color, stability, morphology, solubility, and bioavailability. Therefore, crystal polymorphism is an important and fascinating aspect of solid state chemistry with implications for various fields including pharmaceuticals, materials science (e.g., energetic materials, dyes and pigments, and organic electronics), and agriculture. Late-appearing polymorphs are crystalline forms that emerge unexpectedly after a long period of time or under altered production conditions. Such forms may lead to the inability to obtain a crystal form that was previously prepared for pharmaceutical or other applications, thus necessitate the redesign of the production process. They can alter the solubility, bioavailability, stability, and dissolution rate of the API, significantly impacting the quality, efficacy, and safety of pharmaceutical products. The pharmaceutical industry has suffered a few disastrous issues due to late-appearing polymorphs, leading to patent disputes, regulatory issues, and even market recalls, including the famous cases of ritonavir, rotigotine, 4 and many others. Therefore, it is crucial to identify and characterize all possible polymorphs of a given API and understand the factors that influence their formation and transformation.