Implementing a high-efficiency and high-resolution display has been a primary objective of researchers for the past years. Recently, micro-LED, which is an inorganic light-emitting diode with a size of under 100 μm², has emerged as a promising display technology with its superior features over other displays including liquid crystal displays and organic light-emitting diodes. Although companies have introduced micro-LED displays since 2012, there are still obstacles in mass production. Three major challenges such as low quantum efficiency, time-consuming transfer, and complex color conversion, are covered with their technological breakthroughs in realizing cost-effective micro-LED displays. Methods of improving the degraded quantum efficiency of GaN based micro-LEDs induced by the size effect are introduced which includes wet chemical treatment, adopting passivation layer, optimizing LED structure, and growing LEDs in self-passivated structures. Novel transfer technologies including pick-up transfer and self-assembly methods, for developing large-area micro-LED displays with high yield and reliability are discussed in depth. Quantum dots as color conversion materials for high color purity and deposition methods such as electrohydrodynamic jet printing or contact printing on micro-LEDs are addressed as well.