Sidonie Matsner was the eldest of four daughters and two sons born to a prosperous Austrian-Jewish family. In 1895, they emigrated to the USA, settling in New York City. Sidonie's parents became involved with the Ethical Culture Society and sent her to the Ethical Culture Workingman’s School and later the Ethical Culture Normal School. In 1903, she married Benjamin Gruenberg, a biology teacher, and had four children. The couple also became active in Ethical Culture activities. In 1906, Sidonie Matsner Gruenberg joined the Federation of Child Study, originally a study club of Ethical Culture mothers -- later renamed the Child Study Association of America -- and served as its director from 1923 until her retirement in 1950. She wrote extensively for and about children and parents, and her books were translated into many languages. She was regarded as an authority on child-parent relationships and lectured widely on parent education. She served as a member of the editorial board of Parents Magazine and chaired the subcommittee of the White House Conference on Child Health and Protection in 1930. During World War II, Sidonie and her husband worked to bring German and Austrian relatives out of Europe. In 1967, in her eighties, Sidonie Matzner Gruenberg published the revised edition of her monumental four-volume book The New Illustrated Encyclopedia of Child Care and Guidance.