By CNN Staff
(CNN) -- Jessica Rees was diagnosed with a brain tumor at age 11, and she and her parents would drive to the hospital every day to receive outpatient treatment.
"One day we were leaving, and she just simply asked us, 'When do all the other kids come home?'" said her father, Erik.
When Jessica found out that many of them would have to stay at the hospital, she wanted to help "make them happier, because I know they're going through a lot, too," she said.
So she started making JoyJars -- containers full of toys, stickers, crayons, anything that might brighten a child's day.
"She was really particular about what would go in the jars," said her mother, Stacey. "It had to be something cool, it couldn't be cheap or flimsy."
Jessica created 3,000 JoyJars before she passed away this January. But her parents are carrying on her legacy.