Seeing how surgery and good nutrition can change the lives of people without access to medical care helped Vanessa Perez of Frederick carve her career path. For the past two summers, she served with Mission to Heal, a nonprofit agency that cares for underserved people around the world while training local practitioners. A sophomore at Stevenson University in Baltimore County, Perez went to Liberia the summer before her freshman year, and this past summer, she was in Mongolia.