Electricity is pulsing through Spain and Portugal again after a massive outage knocked out power in both countries on Monday. So too are questions.

An unprecedented blackout across Spain and Portugal upended the lives of millions across the Iberian Peninsula, a stark reminder of modern society's reliance on electricity, and how quickly life can descend into chaos when the grid goes down.

Officials in Spain and Portugal are racing to restore electricity after a huge power outage that grounded flights, paralyzed metro systems, disrupted mobile communications and shut down ATMs, upending the lives of tens of millions of people and turning airports and train stations into campgrounds for stranded travelers