It's been 40 years since Björn Ulvaeus, Agnetha Fältskog, Anni-Frid Lyngstad and Benny Andersson got together in a studio. After releasing their new album, "Voyage," the band is now slated to perform in London this May. Although the so-called "ABBAtar" holograms will replace the original singers, the band members could make an appearance in person.

ABBA's success story began with the song "Waterloo," which they performed at the Eurovision Song Contest in Brighton, England in 1974. From then on, band members Benny Andersson, Agnetha Faltskog, Bjorn Ulvaeus and Anni-Frid Lyngstad started an ABBA craze, which lasted the eight years of their band's existence. ABBA has sold more than 380 million records.

The year before their Eurovision win, ABBA didn't make it into the Swedish pre-selection of the contest. Perhaps this failure made their success the following year with "Waterloo" written by Benny Andersson (left) all the sweeter. Numerous hits followed; songs like "Dancing Queen," "Money, Money, Money," "Super Trouper," and "The Winner Takes it All" remain radio favorites to this day.

In 1977, ABBA went on their first world tour, performing in Europe and Australia, where they had many fans. In the same year "ABBA: The Movie" celebrated its world premiere in Australia. The group also performed for charity, including at the UN General Assembly in New York in 1979 (pictured). Even today, the proceeds from the hit song "Chiquitita," which was performed there, go to UNICEF.

What at first worked so harmoniously in the 1970s — pop music written and performed by two couples who were best pals — became strained by the 1980s. Both couples divorced, and in 1982 ABBA "took a break," as Lyngstad put it. But they haven't gotten back together since. Although two new songs were announced for 2019, they still haven't been released.

The official website of the Eurovision Song Contest announced in the summer of 2020 that five new ABBA songs could be released in 2021, according to the BBC. The band also wanted to go on tour as "ABBAtars" ― with holographic avatars playing on stage instead of the band members themselves.

While Agnetha and Frida have resumed their solo careers in recent years, Benny and Bjorn continued to work together, such as on the stage musical "Mamma Mia!" featuring ABBA songs. The production was turned into the 2008 movie of the same name, with a follow up in 2018 titled "Mamma Mia! Here We Go Again." Ulvaeus and Andersson are shown here at the latter's premiere.

Not many bands have a museum dedicated to them, but ABBA does. In 2013, ABBA The Museum opened in Stockholm and remains immensely popular. Among the interactive installations is a karaoke booth where visitors can record their voices singing along to the hits, and 3D holograms of the band members dancing, which will eventually tour in 2021.

ABBA have also been made into three-dimensional wax figures in the Stockholm Museum, where many of the band's eye-catching costumes can be found. In some parts of the interactive exhibition, visitors can learn the dance moves that go with the music. Once in a while, Frida, Bjorn, Benny or Agnetha even call the museum to talk to the lucky visitor who happen to be closest to the "Ring Ring" phone.

It is ABBA's biggest hit ever. "Dancing Queen" was the second track on their fourth album "Arrival" from 1976. The Swedish band picked up the disco sound that was trending in the US and gave it a Europop twist. "We knew immediately it was going to be massive," member Agnetha Faltskog said. It became a classic that still brings joy to any dance floor.

The winning entry for the 1974 Eurovision Song Contest, this is the song that led to ABBA's worldwide fame. Written specifically for the contest, it was selected as the best song from the competition's history for its 50th anniversary in 2005. Referencing Napoleon's surrender at the Battle of Waterloo, it tells the story of a woman who "surrenders" to the man she loves.

Released in 1975, this was ABBA's first major worldwide hit after "Waterloo." The Who's Pete Townshend called it "one of the best pop songs ever written." John Frusciante, Peter Cetera, Chris deBurgh as well as Portishead are among the musicians who later covered the catchy hit.

ABBA's attitude and outrageous costumes had something uniquely naive that rejoices fans of kitsch to this day. These kimonos were famously worn in the video for "Money, Money, Money." By the time this single from the album "Arrival" was released in 1976 after "Dancing Queen," ABBA was definitely very rich. That didn't matter, as everyone agreed, it "must be funny, in the rich man's world."

Released in 1976, this single became one of the best-selling tracks of all time. The song tells the story of two veteran freedom fighters from the war between Texas and Mexico meeting again: "There's no regret, If I had to do the same again, I would, my friend, Fernando..." Bjorn Ulvaeus once said he liked to write "little stories" with his songs.

"Breaking up is never easy..." This 1977 song is one their first to deal with the break-up of a relationship, years before it would become their own reality. ABBA was composed of two married couples: Agnetha Faltskog was with Bjorn Ulvaeus and Anni-Frid Lyngstad with Benny Andersson. Both of their marriages collapsed at the height of their popularity.

Reflecting the end of a romance, this 1980 track has an aura of sadness that appeared as difficulties in the members' relationships arose. Bjorn Ulvaeus and Agnetha Fältskog announced they were divorcing in 1979, Anni-Frid Lyngstad and Benny Andersson in 1981. However, the band kept touring together. Ulvaeus, who wrote the lyrics, has often claimed the song was not based on his own experience.

This 1975 chart-topper became the title of a musical based on ABBA's songs and musical romantic comedy starring Meryl Streep. "Mamma mia" is Italian which literally translates as "My mommy," but is used to express surprise or excitement.

The title of this 1979 song also borrows from another language, as "chiquitita" is a Spanish term of endearment for a woman meaning "little one." In contrast to ABBA's disco hits, this track opens with a lullaby feel; its chorus is powerful ear candy, "Chiquitita, you and I know..." The video shows the band members singing with a huge snowman.

This time with a title from French, "Voulez-Vous," means "do you want" and is a disco track that appeared on the 1979 album of the same name as well as on many compilation albums. ABBA never officially announced that it had dissolved, but the band stopped being active as a group in 1982. Now they've announced they would be releasing their first new material in 35 years.