Libraries are constantly challenged to find ways to demonstrate their value to their institutions. Can hosting a National Library of Medicine (NLM) exhibition increase a library's impact? In 2012 the University of Toledo engaged their constituents by hosting and developing programming for the NLM exhibit Harry Potter's World: Renaissance Science, Magic and Medicine. The process is synthesized into five stages: choosing, visioning, finding allies, budgeting, and marketing. Recommended practices for each stage are presented. Measures of impact (attendance, views, tweets, feedback) are discussed. Author concludes that hosting NLM exhibitions can be cost effective ways to advance a library's mission, improve visibility and user's perceptions. (Contains 6 figures.)