The CNS role preceded that of the NP in the United States. While CNSs have always been educated to master's degree level, NP education has been more varied although it is now predominantly at this level too. An APN with a master's degree in nursing can attend a post-master's degree certificate programme to obtain education in a new specialty area or to change roles. Emergency care is one clinical specialty area in which NPs and CNSs can obtain education specific to their area of practice. To function in the APN role, nurses must be licensed as registered nurses, have graduated from a NP or CNS educational programme and then have obtained state approval. Certification in the specialty may be required to obtain state approval. Nurse practitioners in emergency care have a scope and standards of practice although these are currently under development for CNSs in emergency care. Nurse practitioners function in roles where they provide direct patients care. Since the CNS role focus is improving nursing care, these individuals typically provide direct care to patients with complex health problems but also focus on care systems.