NASA Organization Structure as of April 2014

Office of the Administrator
  Administrator
  Associate Administrator
       Deputy Associate Administrator
  Chief of Staff
  Deputy Chief of Staff
       Office of Evaluation
  Associate Deputy Administrator
  Associate Deputy Administrator, Strategy & Policy
       Office of Strategy Formulation
  Assistant Associate Administrator
Advisory Groups 
  NASA Advisory Council (NAC)
    Chairman
  Aerospace Safety Advisory Panel (ASAP)
    Chairman
Office of the Inspector General 
    Inspector General
Administrator Staff Offices 
    Chief Engineer
    Chief Financial Officer
    Chief Information Officer
    Chief Scientist
    Chief Technologist
    Chief Health and Medical Officer
    Chief, Safety and Mission Assurance
    Diversity and Equal Opportunity
            Associate Administrator
    Education
           Associate Administrator for Education
    International and Interagency Relations
            Associate Administrator
    General Counsel
    Legislative and Intergovernmental Affairs
            Associate Administrator
    Office of Communications
            Associate Administrator
    Small Business Programs
            Associate Administrator
Mission Directorates
    Aeronautics Research
            Associate Administrator
    Human Exploration and Operations
            Associate Administrator
    Science
            Associate Administrator
    Space Technology
            Associate Administrator

Mission Support Directorate
    Mission Support Directorate
            Associate Administrator
                Human Capital Management
                    Assistant Administrator
                Strategic Infrastructure
                    Acting, Assistant Administrator
                Headquarters Operations
                    Executive Director
                NASA Shared Services Center
                Internal Controls and Management Systems
                    Director
                Procurement
                    Assistant Administrator
                Protective Services
                    Assistant Administrator
                NASA Management Office
                    Director

NASA centers comes in complement of that organigram