Describe your purpose and motivation for pursuing a PhD. Discuss your interest in science, why you want a graduate degree, and your overall professional career goals. Explain briefly how the PIBBS Program at University of Southern California will help you meet your career and educational objectives. If relevant, you may also provide any additional information that you feel the admissions committee should know about your application. This can include unusual academic, family, or personal situations; unexpected challenges or opportunities; unique qualifications; et cetera.