The quantitative determination of the properties of micro- and nanostructures is essential in research and development. It is also a prerequisite in process control and quality assurance in industry. The knowledge of the geometrical dimensions of structures in most cases is the base, to which other physical and chemical properties are linked. Quantitative measurements require reliable and stable instruments, suitable measurement procedures as well as appropriate calibration artefacts and methods. The seminar «NanoScale 2004» (6th Seminar on Quantitative Microscopy and 2nd Seminar on Nanoscale Calibration Standards and Methods) at the National Metrology Institute (Physikalisch-Technische Bundesanstalt PTB), Braunschweig, Germany, continues the series of seminars on Quantitative Microscopy. The series stimulates the exchange of information between manufacturers of relevant hard- and software and the users in science and industry. Topics addressed in these proceedings are a) the application of quantitative measurements and measurement problems in: microelectronics, microsystems technology, nano/quantum/molecular electronics, chemistry, biology, medicine, environmental technology, materials science, surface processing b) calibration & correction methods: calibration methods, calibration standards, calibration procedures, traceable measurements, standardization, uncertainty of measurements c) instrumentation and methods: novel/improved instruments and methods, reproducible probe/sample positioning, position-measuring systems, novel/improved probe/detector systems, linearization methods, image processing