Now Playing: Staff Sgt. Giunta to Receive Medal of Honor

Now Playing: Maj. Gen. Campbell on the Surge Strategy

Now Playing: How 'Star Wars' fans Donald Glover and Alden Ehrenreich prepped for 'Solo'

Now Playing: A dog 'adopted' these ducklings after their mom disappeared

Now Playing: 'Deadpool 2' star Ryan Reynolds on how Celine Dion got involved with the soundtrack

Now Playing: 'Dear White People': Inside the series taking on what it means to be black in America

Now Playing: Up close and personal with the Hawaii volcano spewing lava

Now Playing: How the royal wedding might usher in a new era for the monarchy

Now Playing: This London bus tour offers royal wedding sightseeing with tea service

Now Playing: Texas school shooting survivors on what happened when alleged gunman opened fire

Now Playing: 'American Idol' crowns a new winner: Maddie Poppe

Now Playing: Prince William, Prince Harry greet well-wishers ahead of royal wedding

Now Playing: 10 victims dead in Texas school shooting, explosives found, officials say

Now Playing: Meghan Markle's mom meets Prince Harry's immediate family for first time

Now Playing: How Diana, Kate and Meghan created their own unique fashion statements

Now Playing: Behind the big money-making business of royal wedding souvenirs and merchandise

Now Playing: Kanye West speaks out on politics, slavery and more

Now Playing: From donkey milk to snail mucus, the secret behind the rising popularity of K-Beauty

Now Playing: Former NFL cheerleaders say they're fighting back against gender discrimination

Now Playing: Adam Rippon on skipping the White House visit