The International Year of Light and Light-based Technologies 2015 or International Year of Light 2015 (IYL 2015) was a United Nations observance that aimed to raise awareness of the achievements of light science and its applications, and its importance to humankind. Under the leadership of UNESCO, the IYL 2015 brought together hundreds of national and international partners to organize more than 13,000 activities in 147 countries. The audience reached by the IYL 2015 is estimated to be over 100 million.