"Hidden populations" refer to groups of individuals who are not easily identifiable or accessible due to various factors such as stigma, legal issues, or social isolation. These populations may include individuals involved in substance use, sex work, or those experiencing homelessness. Because they often operate outside of mainstream society, gathering accurate data about them can be challenging. Researching hidden populations is crucial for understanding their needs and providing appropriate services. Public health initiatives, social programs, and policy-making can benefit from insights into these groups, ensuring that they receive the support and resources necessary to improve their well-being and integration into society.