There's one important source that I did not cover in my recent series on energy, because it has not yet proven to be commercially viable, is nuclear fusion. Fusion is the process that occurs in stars. As small atomic nuclei fuse together to make heavier nuclei, energy is produced. Nuclear fusion could prove to be an incredible source of energy, since the fuel source, hydrogen, would be readily available from ocean water, and the byproduct, helium, is environmentally benign. Unfortunately, it has so far been difficult to contain and perpetuate the fusion reaction process. One important step in bringing the promise of fusion to fruition is the ITER reactor being built as an international cooperative project in France. So far, though, this project has run into technological, budgetary, and bureaucratic problems, as described in a recent Scientific American article. That article was illustrated with a LEGO model of the ITER reactor by Sachiko Akinaga, and the Scientific American blog has more photos.