Deep beneath the hillsides and suburbs of Brazil, there are tunnels so vast and regular that they look like abandoned subway ...

The etymology of mistletoe — a plant with small, oval evergreen leaves and waxy white berries — may strike some as repugnant.

The winter solstice is the astronomical start of winter in the Northern Hemisphere, when the North Pole is tilted farthest from the Sun, giving the shortest day and longest night of the year.

The oldest bat skeletons in the world have been identified as a new species, helping scientists fill in the spotty fossil record of these flying mammals and providing new clues about how they evolved.