Why do leaves look so beautiful in autumn?

It's autumn all around the world (minus the southern hemisphere). Just like trees in the United States, the plants in this stunning Israeli vineyard are starting to change color.

Technically, these leaves aren't changing from green to red and yellow. Rather, it's chlorophyll — the chemical that makes leaves green — that breaks down as plants shed their leaves when they sense cold weather. The reds and yellows were always there, but now that green isn't covering them up anymore, you can actually see them.