Spurred on by the invention of the blue light-emitting diode ( LED) a quarter of a century ago, the LED industry has advanced dramatically and has revolutionized the signaling/signage, mobile and flat panel display, and more recently, general lighting markets. Indeed, LEDs now out-surpass in performance all conventional (e.g., incandescent, fluorescent, high-intensity discharge) light sources in general illumination applications. The question arises: what more is to be done? Thus comes the thesis for this special issue on LEDs and applications. From the contributed articles, we learn that LED technology continues to evolve and transform itself not only within the existing applications but is also positioning for brand new applications to come, both of which are highlighted here. (C) 2017 Chinese Laser Press