Carbon nanotubes have excellent electrical properties that make them one of the most promising building blocks for future nanotechnologies. The performances of individual devices, in particular field-effect transistors, already compete favorably with standard CMOS devices. However, there are still some serious issues that remain to be solved before a viable technology could be developed. In particular, the main concern regards the controlled synthesis and positioning of nanotubes. The combination of their electrical properties with their chemical, mechanical and/or thermal properties has already opened very promising routes toward new type of applications in electronics.