This special issue of Materials Science Forum contains the papers which were presented at the 1st International Meeting on Applied Physics (APHYS-2003), held in Badajoz (Spain), and more specifically, the selected papers which were presented during the conference sessions on Interfaces in Colloidal and Particulate Systems, covering Imaging Techniques, Microscopy; Nanoscience and Nanotechnology, Bioengineered Materials, Applied Materials Science / Solid State Physics & Chemistry / Advanced and Functional Materials and Semiconductor Materials and Devices.Volume is indexed by Thomson Reuters CPCI-S (WoS).Applied Physics is seen not really to be a branch of Physics, but rather the application of all of the many branches of Physics to the broad realm of practical problems in Science, Engineering and Industry. This conference was a truly multi-, and inter-disciplinary, event. The organizers had called for papers which related Physics to other sciences such as Biology, Chemistry, Information Science, Medicine, etc, or which combined various areas of Physics; all with the aim of solving practical problems. In other words, the Conference specifically encouraged work which applied the techniques, training and culture of Physics to research areas which are usually associated with other scientific and engineering disciplines. It is a volume which one truly cannot afford to miss reading.