The corresponding chapter in the first edition of this book [1] was written in the mid1990s, at a time when a prominent scientific laser manufacturer had advertised its latest optical parametric oscillator (OPO) with the motto “Good-bye to Ti: and Dye,” signaling the possible demise of tunable dye lasers that had served laser spectroscopists and others well for at least 20 years [2,3]. At that time, a book review speculated that solid-state tunable lasers “might relegate the dye laser to the pages of the history book,” counterpoised by a view that “the dye laser in its many incarnations looks set to be with us for quite some time yet” [4]. Approximately 15 years later, the corresponding chapter in the second edition of this book [5] recorded that Ti:sapphire and dye lasers continued to occupy a significant place in the tunable laser market alongside many others (such as diode and quantum cascade lasers), but that solid-state nonlinear optical (NLO) devices, such as OPOs, were by then preferred as tunable coherent light sources for many spectroscopic purposes in the ultraviolet (UV), visible, near-infrared (IR), and mid-IR [6,7]. The same is true at the time of preparation of this updated chapter (~20 and ~5 years, respectively, after our contributions to the first [1] and second [5] editions of this book), although the spectroscopic dye laser market continues to contract substantially.