It may sound like something out of a Popeye cartoon, but MIT researchers are building a promising solar cell from spinach. In their Cambridge lab, bioengineer Shuguang Zhang and electrical engineer Marc Baldo shine a laser beam on a chip the size of a postage stamp. Out of a wire electrode hooked to the chip comes electricity -- a trickle now, but one day, perhaps, enough to power a cell phone or laptop. Instead of the silicon found in most solar cells, however, this chip uses proteins from plants that have evolved over millions of years to turn sunlight into usable energy.

The advance "is of tremendous importance," says Peter Peumans, an expert on organic electronics at Stanford University, because solar cells that draw on plants' natural photosynthetic ability could eventually be lighter, cheaper, and easier to repair than their conventional cousins.