This text examines the technology behind the plethora of modern industrial and domestic technologies that incorporate micro-optics. It includes a simple but comprehensive introduction to micro-optical element design and an overview of fabrication and replication technologies. It provides the theoretical background and an overview of the technology, with several chapters taking a deeper look at specific applications. The book concentrates on diffractive and refractive micro-optical elements, such as lenses, fan-out gratings, optimized phase elements, and polarizers. It also includes sections on design simulation and optimization and the transformation from design to real optical elements.