The use of thermoelectric technology is attractive in many potential applications, such as energy scavenging from waste heat. The basic principles for harvesting electricity from a temperature gradient were first discovered around 180 years ago, but the contemporary technology utilising inorganic semiconductors was only developed since the early 1950s. The widespread use of this platform has so far been limited by a combination of relatively low efficiency in energy conversion or by issues related to the utilisation of rare, expensive and/or toxic elements that can be difficult to process. Recently much interest has been focused on the use of organic materials in thermoelectric devices, prompted by the possibility of developing large-area, low-cost devices. Considerable research in the last 20 years has been focused on understanding and improving organic thermoelectric properties, with remarkable progress recently published for compounds such as PEDOT and others. Here we provide an overview into thermoelectricity, from the initial discoveries made by Johann Seebeck to modern practical applications including the current trends in organic thermoelectric research.