A clinical nurse specialist (CNS) is an avanced practice nurse, with graduate preparation (earned master's or doctorate) from a program that prepares CNSs. CNSs are clinical experts in the diagnosis and treatment of illness, and the delivery of evidence-based nursing interventions (ANA, 2004). CNSs work with other nurses to advance their nursing practices and improve outcomes, and provide clinical expertise to effect system-wide changes to improve programs of care. The three domains of CNS practice, known as the three "spheres of influence" are the patient/family, nursing personnel and system/network organization. The three spheres are overlapping and interrelated, but each sphere possesses a distinctive focus. In each of the spheres of influence, the primary goal of the CNS is continuous improvement of patient outcomes and nursing care.