5 Things to Know This Morning

— -- Your look at the five biggest and most buzz-worthy stories of the morning.

1. Serena and Venus Williams Face Off at US Open

To pull off a coveted Grand Slam, Serena Williams will have to go through with her sister Venus Williams in the U.S. Open quarterfinals today.

Serena Williams, the No. 1 ranked player in the world, has won 21 Grand Slam titles during her 20-year career. If she wins the U.S. Open, she will be the first person since 1988 to have pulled off the legendary Grand Slam, winning all four Opens in a calendar year.

Serena Williams, 33, told The Associated Press she wasn’t expecting an easy match against her sister, 35.

"It's like playing a mirror,” she said.

2. Greece Picks up Nearly 500 Migrants Overnight

Greece's coast guard says its patrol vessels picked up nearly 500 migrants in 11 search and rescue missions over the past 24 hours in the eastern Aegean Sea. The people, whose nationalities were not immediately clear, were found in small boats near the islands of Lesbos — which accounts for nearly one in two migrant arrivals in Greece — Samos, Kos and the islet of Agathonissi.

More than 15,000 refugees and migrants are stranded on Lesbos, awaiting screening before they can board a ferry to the Greek mainland — from where they head north through Macedonia, Serbia and Hungary to seek asylum in more prosperous European countries.

3. US Dentist Who Killed Cecil the Lion Set to Return to Work

A Minnesota dentist who experienced a global backlash after killing Cecil the lion is expected to return to work after more than a month out of the public eye.

Walter Palmer was named in late July as the hunter who killed Cecil. In following days, he received threats, was vilified online and his office was the site of protests.

In an interview Sunday with The Associated Press and Minneapolis Star Tribune, Palmer said he feels safe enough to return to work Tuesday. He said his staff and patients want him back.

4. Hidden Prehistoric Monument Discovered Near Stonehenge

Researchers have discovered evidence of standing stones believed to be the remnants of a major prehistoric stone monument near the Stonehenge ruins.

University of Bradford researchers said Monday the monument is thought to have been built around 4,500 years ago.

5. Sam Smith Sings New James Bond Theme Song for 'Spectre'

The choice was shrouded in mystery and denials, but British singing sensation Sam Smith has surfaced as the theme song singer for the new James Bond film, "Spectre."

He had denied the rumors, but came clean Tuesday, tweeting that taking part in the Bond film was "one of the highlights of my career."

The 23-year-old who has shot to stardom said he is excited to be part of the film.