While it may not be as simple as pouring water into a gas tank, water, or at least the hydrogen that makes up water, will one day become a significant source of energy. In this important new book, children will discover not only what hydrogen is, but also how this simple element can create clean energy. Hydrogen's past deals with hot air balloons and airships, its present, space shuttles and fuel cells. What fascinating technologies await its future? Other topics include: