The 2014 Nobel Prize in Physics was awarded jointly to Isamu Akasaki, Hiroshi Amano and Shuji Nakamura "for the invention of efficient blue light-emitting diodes which has enabled bright and energy-saving white light sources”. In this talk, I’ll give a brief introduction to LEDs and then discuss the contributions of the three Laureates to the development of the GaN-based light-emitting diode, and explain the issues that caused the blue diode to be developed almost 40 years later than the red LED.