The area of nanoparticle properties and preparation is vast and there are entire journals dedicated to publishing work in this area. In addition, the wide number of potential applications and proposed extensive use and implementation of nanotechnology means that an in -depth analysis of the whole area is beyond the scope of this chapter. Given the broad audience this book is intended for, this chapter aims to provide a comprehensive overview of the area with the purpose of highlighting important issues faced when studying these materials. Review articles have been cited for many of the areas discussed so that the reader may expand their knowledge further by more in -depth reading on areas of specifi c interest. A holistic approach to the content has been adopted to provide the reader with an overview of the key areas pertinent to the subject regardless of background.To achieve this, what a nanoparticle is and what it is not is discussed fi rst. What properties of nanoparticles are key to their function are then examined and some of the unusual properties these particles may possess are highlighted. The challenges facing nanoparticle production are then examined, taking a closer look at several common methods. The preparation of some common types of nanoparticles is discussed and, fi nally, the application of these nanoparticles in devices and formulations is reviewed. This approach is designed to aid the full understanding of the function and properties of the nanomaterials in their fi nal applications.