NIST Physical Measurement LabData related to national standards of length, mass, force, shock, acceleration, time, frequency, electricity, temperature, humidity, pressure, vacuum, liquid flow, and gas flow, as well as electromagnetic, optical, microwave, acoustic, ultrasonic, and ionizing radiation. PML establishes methods and standards for different radiations, investigates the structures of atoms and molecules, develops metrology, and examines the properties of fluids and solids.