Meredith Grey, played by Ellen Pompeo, says goodbye on 'Grey's Anatomy' tonight: Exclusive look

Tonight's episode of "Grey's Anatomy" is a big one: Meredith Grey, played by Ellen Pompeo since the show premiered 19 seasons ago in 2005, is saying goodbye.

The midseason premiere of the long-running ABC medical primetime drama, an episode titled "I'll Follow the Sun," sees our favorite Grey Sloan docs come together to bid a fond farewell to Meredith, who has appeared in more than 400 episodes. Watch "Good Morning America's" exclusive look at the final episode in the media player above.

She's leaving Seattle and moving to Boston to prioritize her daughter Zola's needs to attend a school for exceptionally gifted students as well as taking a job researching for an Alzheimer's cure with the Catherine Fox Foundation.

Another aspect of the episode teased in previews is a nostalgic trip down memory lane for fans of "Grey's Anatomy," seeing moments all the way from the 2005 pilot episode to now.

There are appearances by Meredith's late husband Derek Shepard (Patrick Dempsey) and her best friend Cristina Yang (Sandra Oh) as well as the quotes most associated with those characters, including Meredith telling Derek, "Pick me. Choose me. Love me," and Cristina telling Meredith, "You're my person."

In a November Instagram post, Pompeo teased that this won't be the last time viewers will see Meredith Grey -- she's staying on as executive producer and will continue providing voiceovers for future episodes.

"I am eternally grateful and humbled by the love and support you have all shown me, Meredith GREY and the show for 19 seasons!" the actress, 53, said in the message to fans.

MORE: Ellen Pompeo sends message to 'Grey's Anatomy' fans ahead of departure

Ellen Pompeo shared a message to "Grey's Anatomy" fans ahead of her departure, promising she'll "definitely be back to visit."

The actress said she's going to focus on spending time with her family, including husband Chris Ivery and their three children, as well as starring in a limited series for Hulu this spring.

Series star Chandra Wilson (Miranda Bailey) -- who has been right by Pompeo's side since the beginning -- told "Good Morning America" that Pompeo's departure is a "momentous" move for one of TV's most beloved characters.

"It's definitely historic for the character, and for what that means to the show that carries her last name as the title," she said.

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A teaser for the episode shows a blink-and-you-miss-it moment between Meredith and Bailey, one that's sure to tug at fans' heartstrings. Though Wilson remained tight-lipped on what happens in the scene between her and Pompeo, she teased, "It was certainly an interesting journey to find the right words."

With Pompeo's departure, it leaves Wilson and James Pickens Jr., who plays Richard Webber, as the last two remaining stars who have been series regulars since the beginning of "Grey's Anatomy."

"We're very, very aware of our position as mentors, of our position as people that help everybody else navigate through what dramatic series television is and what it could be," Wilson said. "We get to continue and grow the tradition that was started 19 seasons ago."

"Grey's Anatomy" returns on Thursday, Feb. 23, at 9 p.m. ET on ABC.

ABC Owned TV Stations contributed to this report.