Marie Sophie Schwartz, née Birath, was born in Borås, Sweden. She was the illegitimate daughter of Albertina Bjork, a domestic servant, and Carl Birath, a German merchant who died before she was born. When she was about 18 months old, she was adopted by a relative in Stockholm, a customs official named Trotzig. Wealthy relatives paid for her education in a girl's school from age 14. In 1840, she began living with Gustav Magnus Schwartz, a married physics professor. They had two sons together. She began writing but due to Prof. Schwartz's objections, did not publish until 1851. She made her literary debut that year under the pseudonym Fru M.S.S., and became a highly prolific writer and the most successful in Sweden. Her works were translated into numerous other languages. She wrote a large number of light novels with a strong social slant, often favoring women's emancipation or the rights of workers. Her best known novel was Mannen av börd och kvinnan av folket (The Man of Noble Birth and the Woman of the People, 1858). She also wrote articles for magazines and newspapers.