Soft matter (or soft condensed matter) refers to a group of systems that includes polymers, colloids, amphiphiles, membranes, micelles, emulsions, dendrimers, liquid crystals, polyelectrolytes, and their mixtures. Soft matter systems usually have structural length scales in the region from a nanometer to several hundred nanometers and thus fall within the domain of "nanotechnology". The soft matter length scales are often characterized by interactions that are of the order of thermal energies so that relatively small perturbations can cause dramatic structural changes in them. Relaxation on such long distance scales is often relatively slow so that such systems may, in many cases, not be in thermal equilibrium.

Soft matter is important industrially and in biology (paints, surfactants, porous media, plastics, pharmaceuticals, ceramic precursors, textiles, proteins, polysaccharides, blood, etc.). Many of these systems have formerly been grouped together under the more foreboding term "complex liquids." A field this diverse must be interdisciplinary. It includes, among others, condensed matter physicists, synthetic and physical chemists, biologists, medical doctors, and chemical engineers. Communication among researchers with such heterogeneous training and approaches to problem solving is essential for the advancement of this field.

Progress in basic soft matter research is driven largely by the experimental techniques available. Much of the work is concerned with understanding them at the microscopic level, especially at the nanometer length scales that give soft matter studies a wide overlap with nanotechnology.

This volume presents detailed discussions of many of the major techniques commonly used as well as some of those in current development for studying and manipulating soft matter. The articles are intended to be accessible to the interdisciplinary audience (at the graduate student level and above) that is or will be engaged in soft matter studies or those in other disciplines who wish to view some of the research methods in this fascinating field.

The books have extensive discussions of scattering techniques (light, neutron and X-ray) and related fluctuation and optical grating techniques that are at the forefront of soft matter research. Most of the scattering techniques are Fourier space techniques. In addition to the enhancement and widespread use in soft matter research of electron microscopy, and the dramatic advances in fluorescence imaging, recent years have seen the development of a class of powerful new imaging methods known as scanning probe microscopies. Atomic force microscopy is one of the most widely used of these methods. In addition, techniques that can be used to manipulate soft matter on the nanometer scale are also in rapid development. These include the above-mentioned scanning probe microscopies as well as methods utilizing optical and magnetic tweezers. The articles cover the fundamental theory and practice of many of these techniques and discuss applications to some important soft matter systems. Complete in -depth coverage of techniques and systems would, of course, not be practical in such an enormous and diverse field and we apologize to those working with techniques and in areas that are not included.

Soft matter research is, like most modern scientific work, an international endeavor. This is reflected by the contributions to these volumes by leaders in the field from laboratories in nine different counties. An important contribution to the international flavor of the field comes, in particular, from x-ray and neutron experiments that commonly involve the use of a few large facilities that are multinational in their staff and user base. We thank the authors for taking time from their busy schedules to write these articles as well as for enduring the entreaties of the editors with patience and good (usually) humor.

R. Borsali R. Pecora

September 2007