21

The composition of 21 began in April 2009, while Adele was still in the relationship that inspired the album. Initially, she aimed to create a more optimistic and contemporary sound, but the studio sessions were not fruitful. It was after the separation that the production came to life, channeling her sadness into the songs. She collaborated with several producers and songwriters, including Rick Rubin, Paul Epworth, and Dan Wilson, which brought a diversity of styles to the tracks.

The impact of 21 was monumental, surpassing the commercial expectations of her independent label, XL Recordings. The album reached number one in over 30 countries and became the best-selling album worldwide in 2011 and 2012. In the United Kingdom, it is the best-selling album by a solo artist and has held the record for 23 weeks at the top of the albums chart, a feat that sets it apart among female artists. In the United States, it remained at number one on the Billboard 200 for 24 weeks, setting a new record for a female artist. With over 31 million copies sold, 21 is not only one of the best-selling albums of the 21st century but has also been praised for its subtle production and Adele's powerful vocal performance. Among its standout singles are "Rolling in the Deep," "Someone Like You," and "Set Fire to the Rain," all of which reached number one on various international charts, reaffirming its universal connection with audiences.