In the mid-19th century, the Harvard Observatory began hiring women as calculators to interpret the results of nightly astronomical observations performed by men. At first these were the wives, sisters and daughters of the observatory's staff astronomers, and then they were joined by graduates of women's colleges. When photography entered astronomical practice, women, in addition to calculations, began to study the stars captured at night on glass photographic plates. The “Glass Universe” of half a million photographic plates accumulated at Harvard over decades allowed women to make remarkable discoveries that received worldwide recognition. They helped to understand what stars are made of, classify them and find a way to determine interstellar distances. The book contains a lot of interesting facts, it contains many excerpts from letters, diaries and memoirs. In fact, this is the story of women whose contributions to science changed our understanding of the stars and humanity's place in the Universe. The employment opportunities provided to women at the Harvard Observatory beginning in the late 19th century were atypical for a scientific organization, especially for such a male stronghold as Harvard University. Features The book contains an insert with photographs of views of the Harvard Observatory, with portraits of employees, directors and group photographs. The large female staff, which was sometimes mockingly called a “harem,” included representatives of all ages. They were distinguished by either success in mathematics, or a love of observing stars, or both at the same time. Some were graduates of newly established women's colleges, others had only a school education, but had natural talent. For whom the book is addressed primarily to those who are interested in astronomy and the history of the development of our ideas about the Universe.