The ability to grow uniform and monodisperse crystals is also challenging. Controlling crystal uniformity and morphology is important for applications such as nanoparticles, photonic crystals, and quantum dots. These applications include drug delivery, display technology, and optical switches, to name a few. Seeding and additives have been used to shape crystals. Organic additives or modulators can coordinate selectively the facets of a growing crystal and can affect the morphology, dimension, and crystallographic structure. For example, amino acids have been used to control the shape and size of crystals. Weissbuch, Addadi, Lahav, and Leiserowitz have shown that the crystal morphology of glycine can be controlled by chiral modulators such as (S)-amino acids and (R)-amino acids. These morphological changes occur due to the adsorption of the modulators on particular crystal faces based on the modulator chirality.