The principles and phenomena outlined within this book are the basic concepts of nanochemistry which can lead to intricate and complex designs that form the heart of the many facets of nanoassembly from various nanomaterials. Detection of chemical and biological agents plays a crucial role in medicinal filed, forensic, agricultural, environmental and electronics. Development of sensitive methods which allow identification of toxic metals anions, biological important metal ion and biomarkers such as proteins and nucleic acids provide the prospect of better health, more effective therapy and on site monitoring. A useful sensing system should meet two requirements: satisfactory selective recognition sensing moiety for binding with target analytes and a measurable response process to signal the binding event. The ability of these two components are significantly related to the outcome of the detection process in terms of the response time, sensitivity, selectivity and stability of the system. Thus, the challenges in development of novel detection systems have been concerned with getting better the recognition process as well as designing pioneering assemblies.