Important physical and chemical properties of nanometer scale devices and structures depend on their shape and size. The benefits of nano are already increasing many applications, and are expected to grow significantly. For these applications, measurement accuracy is a fundamental measurement science issue because 1 nm is close to or even below the spatial resolution limit of existing nondestructive measuring instruments. As the nation's leading measurement institute, extending length measurement science and traceability to nanotechnology is part of NIST's mission. Our publications about measuring methods are heavily referenced, and the methods find their way into industry metrology tools and international measurement comparisons. Our measurement methods, reference artifacts and modeling software are used by companies that make metrology tools for nanotechnology applications.