Brock falls in love with her and stays with her during Ash Ketchum's Orange League adventure. Not only did they part on mysterious terms, but the details of Brock's work at her lab have never been fully explained. Whatever happened, speaking Ivy's name around Brock causes him to curl up into a ball and simply state, "Don't mention that name!" The events that caused Brock to be traumatized have been the subject of fan speculation for quite some time.
Professor Ivy's field of research is regional differences in Pokémon physiology.