Complex sentence: In 1988, she began her Postdoctoral Fellowship at Rockefeller University in the lab of Michael Young, where she had her first exposure to the study of circadian rhythms, a field in which she has since remained.
Split into simpler sentences: In 1988, she began her Postdoctoral Fellowship at Rockefeller University in the lab of Michael Young. There she had her first exposure to the study of circadian rhythms, a field in which she has since remained.