The invention of scanning tunneling microscopy, atomic force microscopy and near field optical microscopy has opened up a new field of research: scanning probe methods (SMP). The quality of image acquisition has made great strides in recent times, but many fundamental, unsolved problems remain unanswered about the interaction between probe tip and sample. This text contains 60 contributions dedicated to these problems. Most of the contributions are reviews, presenting condensed, relevant information, suitable for both students and specialists. The contributions cover the instrumental aspects and design of force microscopes in different environments (ambient pressure, low temperature, ultrahigh vacuum, liquids). Theory is also covered, including ab initio calculations and molecular dynamics simulations. Mechanical properties at micro and nanoscales receive intensive treatment, including adhesion, friction and wear. Other highlights include advances in near field optical microscopy and its relation to forces, the application of force microscopy in NMR and the observance of flux lines in high Tc superconductors. Recent advances in biology and chemistry are also addresssed.