By the end of their first year, candidates pursuing an Engineering PhD must have decided on a narrower branch of engineering study such as mechanical engineering, civil engineering, chemical engineering, and so on. Subsequently, they are required to choose a research area within the selected area, conduct extensive research on it, and write a thesis or dissertation based on their research, often supervised by a faculty member. For example, if a candidate has chosen Chemical Engineering as a specialization for the PhD, examples of research areas would be Cellular Engineering, Polymers and Complex Fluids, Sustainable Energy, Materials, Nanotechnology, Biomolecular Engineering, Computing and Simulation, Microfabricated Systems, and Catalysis and Reactions.