Cryptochrome is a type of light-sensitive protein involved in regulating the biological clock and sensing light signals. Family members include CRY1, CRY2, which contain two main domains: a light-sensitive FAD-binding domain and a C-terminal extension domain. Cryptochrome is primarily located in the cell nucleus, where it regulates growth, development, and flowering time in plants, and maintains circadian rhythms in animals. The expression of cryptochrome is tissue-specific, and mutations or dysregulation of its expression are associated with sleep disorders, mood disorders, and metabolic diseases. Cryptochrome influences transcription factors and signaling pathways through both light-dependent and light-independent mechanisms, regulating gene expression and cellular function.