The Institute of Medicine (IOM) and National Research Council's (NRC) 2015 report, Transforming the Workforce for Children Birth to Eight, offers recommendations to build a high quality early childhood workforce with the knowledge, preparation, and support to promote children's development and learning. As the report notes, "Preparation programs, training, mentoring and coaching, and in-service professional development are all critical direct mechanisms for developing and sustaining the knowledge and competencies of professionals." This brief summarizes what the report says about professional development and learning teachers gather during teaching practice. (author abstract)