After covering a plethora of topics in single paragraphs in Chapter 1 (7 pages), the authors devoted Chapter 2 (30 pages) to the basic physics of liquid microlenses—though much of the latter chapter also applies to solid microlenses. Chapter 3 (27 pages) covers fabrication methods that are useful for a wide variety of devices and structures, not necessarily microlenses. Solid microlenses have fixed focal lengths and are therefore not tunable. Techniques for their fabrication are discussed in Chapter 4 (33 pages). Liquid lenses are tunable in a variety of ways. Five types of electrically tunable liquid microlenses are presented in Chapter 5 (35 pages). These include liquid-crystal microlenses, microlenses encapsulated in polymer films, dielectrophoretically tuned microlenses, microlenses tuned by electrowetting, and electrochemically activated microlenses. Glass-membrane microlenses, polymer-membrane microlenses, and hydrogel-activated microlenses exemplify the mechanically tunable liquid microlenses covered in Chapter 6 (33 pages). The integration of horizontal microlenses in microfluidic circuitry is the scope of Chapter 7 (21 pages). The monograph concludes with five avenues for further research presented in Chapter 8 (5 pages).