Centro de Investigaciones en Optica (also known as CIO) is a research center in the field of optics which is a branch of physics. CIO is located in the city of Leon in the state of Guanajuato in Mexico (approximately at 21°09'12.02'N 101°42'15.84'W). It also has an industrial research facility in the city of Aguascalientes. Centro de Investigaciones en Optica (also known as CIO) is a research center in the field of optics which is a branch of physics. CIO is located in the city of Leon in the state of Guanajuato in Mexico (approximately at 21°09'12.02'N 101°42'15.84'W). It also has an industrial research facility in the city of Aguascalientes.