## 1 Introduction  
Significant research efforts in the last years have been dedicated to the design, preparation and characterization of inorganic particle-polymer based composite materials. When such different materials are combined to form heterogeneous structures, the properties of the resulting composite depend on the constituent properties, as well as on the chemical and morphological details of the dispersion. Nanocomposites can be defined as multicomponent materials, in which at least one of the phases has dimension in the nanometer range.  
The extraordinary interest in nanocomposite materials is mainly due to the vast range of properties that can arise from the combination of the peculiar characteristics of each component, nanoparticles (NPs) and host polymer. Indeed, the original size-dependent physical and chemical properties of the NPs, joint with the high processability and defined chemical and morphological structure of the polymers, finally result in innovative materials with unique and tunable characteristics that cannot be achieved by traditional materials. In addition, nanocomposites can also show original properties, not fully envisioned from the properties of the single components, deriving from the local micro-structural arrangements of the nanosized objects in the polymer [1].  
Several routes can be followed for the preparation of a NP based polymer nanocomposite. Among the different approaches recently reported, ranging from _in situ_ methods in which NPs are generated in the polymer matrix, to more general _ex situ_ methods in which NPs that were previously synthesized are incorporated in the polymer matrix, the latter are particularly well suited for a flexible selection of the specific components. By _ex situ_ procedures it is possible to access both a wide range of high-quality NPs, achievable by using the more advanced synthetic routes, to carefully control size and size dispersion, and at the same time, a wide choice of host media is available. This class of nanocomposite preparation is convenient from many perspectives. Indeed, the incorporation of semiconductor, oxide or metal nanocrystals (NCs) allows to convey their inherent functionalities to suitable host polymers, thus providing original nanocomposite materials, with high technological impact in a variety of applications [2, 3] ranging from LED, lasers, non linear optical devices [4, 5] and bio-labeling. Such materials are particularly suited to further processing steps, which is essential for micro- and nano-technological applications to achieve functional materials to integrate in systems and devices. Nevertheless, the relevant issues of aggregation, phase separation and limited dispersion of the nanoscale components in the host phase need to be overcome.  
This review aims to provide a picture of NC-polymer based composite concepts, their preparation methods and finally their use in micro- and nanofabrication. Due to the large extent of the topic, we will mainly concentrate our attention on the preparation and processing of nanocomposite based on _ex situ_ incorporation of colloidal NCs in organic moieties.  
An overview on the complex and various scenario of the nanocomposite properties and preparation strategies will be firstly provided. Next, attention will be paid to the patterning by means of either conventional and emerging micro- and nano-scale processing techniques towards the fabrication of innovative functional devices.