The emergence of the organic semiconductors in the electronics area and the technologies of information is now on a reality. Small molecules or polymers, these materials can be to substitute for silicon in the realization of transistors, photovoltaic cells or electroluminescent diodes. Easy to deposit, mechanically flexible, they are inexpensive. Their structure can be adjusted so as to obtain the desired properties. Lastly, the recent possibility to obtain single crystals of great purity opens vast prospects towards "Plastic Electronics".