Complex sentence: Elsie Lacks (born Lucille Elsie Pleasant), second born and eldest daughter of Henrietta Lacks, who was the source of the famous HeLa cell line, was institutionalized here for epilepsy until she died in 1955 at the age of 15.
Split into simpler sentences: Elsie Lacks (born Lucille Elsie Pleasant) was the second-born and eldest daughter of Henrietta Lacks, who was the source of the famous HeLa cell line. Elsie was institutionalized here for epilepsy until she died in 1955 at the age of 15.