Stevie Nicks has called Harry Styles ‘the son I never had.’ Here's a timeline of their friendship.

• Harry Styles and Stevie Nicks met in 2015 after a Fleetwood Mac concert.
• The two first performed onstage together in May 2017.
• Styles inducted Nicks into the Rock and Roll Hall of Fame as a solo artist.

A few years ago, Harry Styles and Stevie Nicks formed an unlikely friendship that has blossomed into one of the music industry's sweetest pairings.

Since their meeting in 2015, Styles and Nicks have performed together and raved about each other in interviews - the Fleetwood Mac star even called him "the son I never had."

Here's a complete timeline of their friendship so far:

April 2015: They met backstage at a Fleetwood Mac concert

According to the Mirror, Styles met Mick Fleetwood and his daughters backstage at a One Direction concert before ever formally introducing himself to Nicks.

In 2015, Styles met the "Silver Springs" singer after a Fleetwood Mac show in London when he brought her a birthday cake.

"Piped her name onto it. She loved it," Styles told Rolling Stone in 2017. "Glad she liked carrot cake."

May 19, 2017: Styles brought Nicks onstage with him for the 1st time

During the early legs of his debut album's international tour, Styles surprised his Los Angeles crowd at the Troubadour with an appearance by Nicks.

According to Billboard, Styles initially introduced her by saying, "I'm pretty sure that this was going to be up there with one of the best nights of my life."

"If there was any doubt, I'm pretty sure I'd like to confirm, in my entire life, I never thought I'd be able to say this," he continued. "Please welcome to the stage, Stevie Nicks."

The two performed his song "Two Ghosts," Fleetwood Mac's "Landslide," and Nicks' "Leather and Lace" together.

In a 2020 interview with NPR, Styles said his favorite part of that experience wasn't necessarily the performance, but the practice beforehand.

"When we first played together, it was at the Troubadour ... and it was an amazing moment, but my favorite was sound checking," Styles said."It's like four people in there and just us singing in the empty Troubadour. For me, that's a moment that I'm going to hold on to."

September 2017: Styles performed 'The Chain' on BBC Radio 1

Throughout the rest of his tour, Styles continued to pay homage to Nicks by performing Fleetwood Mac's "The Chain" at some of his shows.

He also covered the track during his September 2017 appearance on BBC Radio 1.

January 26, 2018: Styles performed onstage with Fleetwood Mac

Fleetwood Mac was honored by a string of performances and speeches at the 2018 MusiCares Person of the Year awards, and Styles introduced the band before their mini-concert at the event.

"There are several things I thought I would never be doing in my life," Styles said. "One is sharing the stage with these legends ... let alone having the honor of introducing them to the stage."

Unlike several of the other musicians who covered the band's hits on their own, Styles joined Fleetwood Mac for their performance of "The Chain."

February 2019: Nicks called Styles 'the son I never had'

In a 2019 interview with Rolling Stone, Nicks called Styles her and Fleetwood's "love child."

"When Harry came into our lives, I said, 'Oh my God, this is the son I never had.' So I adopted him," she said. "I love Harry, and I'm so happy Harry made a rock-and-roll record - he could have made a pop record and that would have been the easy way for him."

March 29, 2019: Styles inducted Nicks into the Rock and Roll Hall of Fame as a solo artist

Although Nicks was already inducted into the Rock and Roll Hall of Fame as a member of Fleetwood Mac, she received the honor again as a solo artist in March 2019.

Styles formally inducted the "Leather and Lace" singer, calling her "a beacon to all of us."

"Whenever you hear her voice, life gets a little bit better," Styles said in his speech. "When she sings, the world is hers, and it is yours. She is everything you've ever wanted in a lady, in a lover, in a friend."

"... She is both an adjective and a verb," he continued. "To quote my father, 'That was rather Stevie Nicks.' And to quote my mother, 'I Stevie Nicksed that s--- so hard.'"

Styles and Nicks also performed her and Tom Petty's duet, "Stop Draggin' My Heart Around."

After the event, Nicks talked about Styles and accidentally mixed up his former boy band, One Direction, with NSYNC. Realizing her error, she said she's "never gonna live that one down."

May 2019: The duo performed together again at an after-party in Rome

After the Gucci Cruise 2020 fashion show in Rome, Styles and Nicks graced the stage together and performed "Landslide" and "Stop Draggin' My Heart Around."

December 13, 2019: Nicks and Styles took the stage together again during one of his shows

Later that year, the two performed "Landslide" together yet again during one of Styles' "Fine Line" shows at the LA Forum.

Rolling Stone reported that Styles introduced Nicks by saying, "I have a feeling that you're going to enjoy this as much as me. She has been a light for me, and I'm sure she's been a light for every single one of you."

Nicks posted a video of their performance on Instagram, writing that she was "honored" to share the stage with him and congratulating him on a "beautiful record."

February 2020: Styles called working with Fleetwood Mac an 'out-of-body experience'

When asked what it was like to work with the rock band and Nicks in a February 2020 interview with NPR, Styles said it bordered "on an out-of-body experience."

"'Dreams' was the first song I knew all the words to; I used to sing it in the car with my mom," Styles said. "Every time I'm with her, you want to be, obviously, present, right?"

"I'm trying to enjoy being with her and soaking it in," he added. "But at the same time, when you're in the room with her, I'm sitting there thinking about being 10 years old and singing the song."

March 2020: Styles said that Nicks was one of the 1st people to listen to 'Fine Line'

In a March 2020 interview on "The Howard Stern Show," Styles said that Nicks was one of the first people to hear his sophomore album.

After he took her out to dinner, Styles played the record for Nicks and her friend group, or "little witches' coven," during the early hours of the morning.

"So it's getting to like 3 a.m. playing the album, I'm like, 'I'm kinda tired' and they're like right in their prime," Styles said. "They're really like, 'Oh, this is like daytime for us.'"

The "Watermelon Sugar" singer also shared that Nicks urges him "just do what I want to do," but Styles didn't take all of her advice after the initial listen.

"So, there's a couple bits where like, she thought the first single was wrong, and she thought a song that didn't go on the album should've gone on the album," Styles said. "... I guess the feeling for me becomes, 'OK, well, if I wanted it this way, and then she told me to change it - and I didn't - I must really want it this way.'"

March 2020: Nicks shared that Styles had inspired her to write new music

When the coronavirus pandemic began sweeping the US in March 2020, Nicks updated her followers with an Instagram post in which she shared that she was trying to be creative.

She wrote that she was mostly listening to Styles' album and was "inspired by him" to write new music and poetry.

April 2020: Nicks said she was spending time in quarantine listening to Styles' music

In an April 2020 interview with Rolling Stone, Nicks confirmed she was listening to "Fine Line" a lot during quarantine.

She compared the experience to enjoying Crosby, Stills and Nash's debut album or Joni Mitchell's "Court and Spark" when they first came out, since she listened to both for six months straight.

"Harry is recounting a lot of experiences that I had in my own life, beautifully," Nicks said. "And making me remember stuff, and bringing back memories that I really didn't love and memories that I did love."

"For me to hear a record made by somebody in his mid-20s that says a lot of things that I haven't gotten around to saying yet blows my mind," she added.

September 2020: Nicks said she wanted Styles to star on her TV show

Nicks is working on a TV miniseries based on Evangeline Walton's adaptation of the Celtic deity that inspired her song "Rhiannon." And in September 2020, she told the LA Times that Styles "is definitely in the running" for a starring role.

"I'm going, 'Harry, you cannot age one day. You have to stay exactly as you are,'" she said. "I've already sold him on it."

October 2020: Nicks said Styles is so funny 'he could actually have a TV show'

When asked about her friendship with Styles in an October 2020 interview with British Vogue, Nicks called the "Adore You" singer an "amazing man."

"He's so talented, he is a really, really great artist, and he's so funny," she said. "He could actually have a TV show, like James Corden or Johnny Carson - he could do that. When you're with Harry Styles, you're not with a famous person, he's just Harry."

November 2020: Nicks spoke about Styles in a Vogue Q&A

In honor of Styles' status as the first solo male cover star of the magazine, Vogue interviewed Nicks about the rock star in November 2020.

The "Landslide" singer told the publication that "Sunflower" is one of her favorite songs of his, she thinks "Fine Line" is his version of Fleetwood Mac's huge success "Rumours," and she's inspired by younger artists like Styles, Miley Cyrus, and Haim.

Nicks also said she gifted Styles a pink-stone ring she owned that she thought "should be for Harry."

"You can see it on his hands in the 'Falling' video where he's playing the piano," she said. "If Harry and I were in a band together, we'd be trading all kinds of crazy stuff."

Nicks also told the publication that they are "open to making music together."

"I would love to be in a band with Harry, but even if I never saw him in person again, he's made a record that breaks my heart in a million places like 'Fine Line,'" she said. "... I'm always ready to slip back into those high-heel black suede boots and become my alter ego."