With the development of new generations of optoelectronic devices that combine high performance and novel functionalities (e.g., flexibility/bendability, adaptability, semi or full transparency), several classes of transparent electrodes have been developed in recent years. These range from optimized transparent conductive oxides (TCOs), which are historically the most commonly used transparent electrodes, over new electrodes made from nano- and 2D materials (e.g., metal nanowire networks and graphene), to hybrid electrodes that integrate TCOs or dielectrics with nanowires, metal grids or ultrathin metal films. In this progress report, we introduce the most relevant transparent electrodes developed to date, describe their fundamental properties, and classify their materials according to specific application requirements in high efficiency solar cells and flexible OLEDs. This progress report serves as a guideline to selecting and developing appropriate transparent electrodes according to intended application requirements and functionality.