(music plays)

In animation, a shooting star flies in space past planet Earth as a title appears: I wonder... WHY?

A boy pops up on screen. He has short blond hair. His name is Alex.

Alex stands under a tree and says HI, I'M ALEX HUDSON.
AND I'M WONDERING
WHY GREEN LEAVES
CHANGE INTO RED
LEAVES AND ORANGE
WHEN IT GETS COLDER?

He shows leaves of different colours.

He says THAT'S MY QUESTION.

Now Kevin Donker appears on screen. Kevin is a perimeter scientist.

Kevin says ALEX, THAT'S A REALLY
GREAT QUESTION.
BELIEVE IT OR NOT, ALL
LEAVES IN THE SUMMERTIME
HAVE DIFFERENT
COLOURS IN THEM.
THEY HAVE GREENS AND
YELLOWS AND REDS.
THE GREENS KIND OF
DOMINATE THE LEAF.

In animation, a close-up of a leaf shows tiny green dots on it. The sun shines into the green dots.

Kevin says THE GREENS ARE FROM LITTLE
BITS OF CHLOROPHYLL.
WHAT CHLOROPHYLL DOES IS
IT TAKES IN SUNLIGHT
AND IT GIVES THE TREE FOOD.
IN THE FALL, WHEN THE
TREE STARTS TO HIBERNATE,
THESE LITTLE BITS OF
CHLOROPHYLL BREAK DOWN
AND THEY DISAPPEAR
FROM THE LEAF.
AND ALL THAT'S LEFT OVER
ARE THE YELLOWS AND REDS.
THAT'S WHY WHEN YOU LOOK
AT A FOREST IN THE FALL,
YOU CAN SEE ALL THESE
BEAUTIFUL COLOURS.
(music plays)