Amy and her brother, Sam, are playing in the local park. Sam brought his new hover toy to try out.
It's difficult to control and Sam falls off, hurting his elbow.
"Ow! That hurts!" he cries.
"Are you OK?" asks Amy, as she helps him up. "Oh no, you've cut your elbow." Sam looked and saw the blood.
"We'll need to clean you up and get a plaster on it," said Amy.
"Why's blood red?" Sam wanted to know.
"It contains iron, that's why", Amy explained.
"What? There's metal in my blood?" asked Sam.
"Come on, let's get you cleaned up," laughed Amy, "then we'll find out all about your blood."