Selena Gomez was doing an interview with "On Air With Ryan Seacrest" in L.A., when Ryan told her about an e-mail he'd receieved from a 13-year-old named Hana with a terminal illness.

Hana was born with a disease called "progeria" which means she ages 8-10 times faster than normal. The average lifespan of someone with this disease is just 13 years, and Hana just turned 13. Only ten people in the whole United States have progeria.

And her biggest dream was to meet Selena because her muziek helps keep Hana strong. Ryan Seacrest zei "I told Selena Hana's story, and she stopped recording her album in the studio and went to meet Hana in the hospital."

Hana was totally shocked door the surprise visit, and her tutor zei "it was the best Christmas ever" for her. What a sweet thing for Selena to do!