Complex sentence: For several years, the impoverished Nevelson and her son walked through the streets gathering wood to burn in their fireplace to keep warm; the firewood she found served as the starting point for the art which made her famous.
Split into simpler sentences: For several years, the impoverished Nevelson and her son would walk through the streets gathering wood to burn in their fireplace to keep warm. The firewood she found would serve as the starting point for the art which made her famous.