The National Academy of Engineering in Washington, D.C., once asked its members to pick the greatest engineering achievement ever.
Their choice? The electrification of the country through what's known as "the grid."
Ernest Moniz, director of the Energy Institute at MIT, says they were right on the money.
"That reflects what an amazing machine this is, spread out geographically, always having to balance demand and supply because electricity is not stored," he says.