"When Toyota puts its considerable bulk behind a new technology, everyone should sit up and take notice."
When it launched the first generation Prius back in 1997, many scoffed.
It was ugly, not terribly efficient and distinctly uncool.
Eighteen years later, Toyota has sold nearly five million Prius's, and it is now the best selling car in Japan. And so enter the Toyota Mirai, the world's first mass-produced hydrogen fuel cell car.
The, now rather tired, joke about hydrogen is that it is "the fuel of the future, and always will be". Fuel cells were invented in the 1880s.
They were used on the Apollo spacecraft back in the 1960s (remember Apollo 13's exploding hydrogen tank?).
A fuel cell works by taking hydrogen fuel and reacting it with oxygen to produce electricity. The only waste product is water.
Read More: 'Big, heavy, expensive'