Is there a way to predetermine your baby's biological sex and conceive a girl or a boy? Here's what science has to say about things like genetics, timing, diet, and even adrenaline.

Light is the fastest moving thing we know of, but just how fast is it? Has science attempted to break the light speed record? And does the universe have a speed limit?

Go to the supplement aisle of almost any store in the US and you'll find melatonin, a synthetic hormone, marketed as an effective natural sleep aid, even for children! But is melatonin actually safe to use? Studies say ...

Not even light can escape a black hole's gravitational pull, so how do we actually know they exist? And what's the deal with the supermassive black hole at the center of the Milky Way?

Spiders, snakes, heights, political corruption—we're afraid of a lot of things. But what's the difference between a fear and a phobia? And can either literally scare you to death?