The scientific, engineering, and medical communities have worked for decades to improve the representation of women in science, technology, engineering, mathematics, and medicine (STEMM). While there has been significant progress, women -- and particularly women of color -- remain underrepresented in many scientific fields and at many levels in education and career stages. On March 11, 2019, the National Academies of Sciences, Engineering, and Medicine held a symposium to examine policies, practices, and strategies that have effectively improved the representation of women in STEMM. This publication highlights the presentations and discussion of the event.