The National Academies has published a report on the science of mentorship, and it is freely available online! While “report” sounds quite technical, this is actually a book whose chapters focus on subjects that include what mentorship is, why identity matters in the STEMM (science, technology, engineering, mathematics, and medicine) fields, the forms mentorship can take, and what can be measured in mentoring relationships. There is a lot of helpful information here, and much of it is data-driven. You need to make a free account on the National Academies Press website to download the free PDF, but it’s worth it!