The late 1990s and early 2000s saw R.E.M. continue to evolve and explore new sounds. (2001) was a melancholic and introspective album that marked a return to the band's earlier sound. Around the Sun (2004) was a more upbeat and atmospheric album, featuring a renewed focus on guitar work. Accelerate (2008) was a high-energy album that saw the band revisiting their earlier sound, while Collapse into Now (2011) was a more experimental and atmospheric album that marked a fitting conclusion to the band's studio discography.