Functionalization of surfaces through the covalent attachment of organic monolayers has many applications in chemical/biological sensing, drug delivery, selective gas separation, cancer detection, etc. In this regard, click chemistry reactions, especially those that require no metal catalyst, are powerful candidates. Click chemistry reactions have unique characteristics such as mild reaction conditions, high yields, high reaction rate, compatibility with different kinds of solvents especially water and easy post-treatment. This book focuses on the functionalization of glass and diamond surfaces via different click reactions with the purpose of creating microscale patterns for different applications. One of the novel aspects of surface functionalization, discussed in this book in detail, is the protein immobilization on the surface in order to construct biosensors which are widely used in the rapid and accurate detection of protein substances such as avidin or cancer biomarkers.