Why are rubies red and emeralds green? Their colors come from the same metal in their atomic structure
The colors of rubies and emeralds are so striking that they define shades of red and green—ruby red and emerald green. But ...
What scientists are learning about how to prevent allergies in kids
Research suggests that introducing kids to food allergens early in life can help—but that the same might not be true for other types of allergies. Here's what to know.