Recognition receptors play a key role in the successful implementation of chemical and biosensors. Molecular recognition refers to non-covalent specific binding between molecules, one of which is typically a macromolecule or a molecular assembly, and the other is the target molecule (ligand or analyte). Biomolecular recognition is typically driven by many weak interactions such as hydrogen bo- ing, metal coordination, hydrophobic forces, van der Waals forces, pi-pi interactions and electrostatic interaction (due to permanent charges, dipoles, and quadrupoles) the polarization of charge distributions by the interaction partner leading to ind- tion and dispersion forces, and Pauli-exclusion-principle-derived inter-atomic repulsion, and a strong, “attractive” force arising largely from the entropy of the solvent and termed the hydrophobic effect. In recent years, there has been much progress in understanding the forces that drive the formation of such complexes, and how these forces are relate to the physical properties of the interacting molecules and their environment allows rational design of molecules and materials that interact in specific and desired ways. This book presents a significant and up-to-date review of the various recognition elements, their immobilization, characterization techniques by a panel of dist- guished scientists. This work is a comprehensive approach to the recognition receptors area presenting a thorough knowledge of the subject and an effective integration of these receptors on sensor surfaces in order to appropriately convey the state-of the-art fundamentals and applications of the most innovative approaches.