All the 787 Dreamliners—Boeing's most advanced passenger aeroplane ever—have been grounded because of what you can see above: a melting battery made by the Japanese company GS Yuasa Corp, integrated in the aeroplane at Boeing Everett Factory, in Everett, Washington. Looks pretty bad to me.
This is not the first time an airliner has been grounded. All Douglas DC-10s were grounded in 1979 after generalised wing damage was discovered following a crash that killed 271 people. The MD-80 was also partially grounded because of faulty wiring.