England's Metropolitan Police now have comprehensive laboratory facilities at New Scotland Yard, and the provinces are served by six operational laboratories administered by the Home Office. Each of the operational laboratories has a full range of scientific services except for firearms investigation and document examination, which are centralized at the Nottingham and Birmingham laboratories respectively. Fingerprint work is conducted by specialist police officers operating within their forces. The Home Office Central Research Establishment at Aldermaston provides the operational laboratories with information services and certain advanced instrumental analysis facilities besides seeking to develop and evaluate new methods and instrumentation for use in routine casework. Significant advances have been made in recent years in methods to group blood and other body fluids. Electrophoretic techniques are used in this work. Gas chromatography, which relies on the dynamic equilibrium of substances between the vapor phase and a solid or liquid phase, is used in drug analysis, blood alcohol analysis, and many areas of chemistry, while automated equipment that has long been used in blood cell counting has been adopted by the forensic scientist for soil particle analysis. Other forensic activities and techniques are the measurement of optical properties, atomic absorption spectrometry, fluorescence, X-ray diffraction and fluorescence, the scanning electron microscope, and mass spectrometry.