It was the year 1990, Jesper decided to take leave of the band Ceremonial Oath, that he was currently in, together with Anders Fridén and Anders Iwers (Tiamat)

He wanted to make music in a different direction, and he teamed up with Johan Larsson and Glenn Ljungström to form IN FLAMES. The gang made a demo and shipped it off to Wrong Again records in order to get a record-deal, which they did. The owner of the company enjoyed the music so much that he immediately gave them a deal over the phone, as they rang him up one night. The next day, they sat down and wrote the album Lunar Strain, which was released some time later, and became a big underground success. They had some "in and out members" , and borrowed some from different bands. People that have been a part of IN FLAMES since the beginning, are Mikael Stanne and Anders Jivarp (Dark Tranquillity), Anders Iwers (Tiamat), Henke Forss (Dawn), Daniel Erlandsson (Eucharist, Arch Enemy), and a few more. The band then released a mini-CD called Subterranean, that became the "breaker" for IN FLAMES, in terms of getting out off the underground scene, that is, and led them to get a license deal with German company Nuclear Blast for the next record, and they have been there since then. After some time, the boys were getting tired of constantly borrowing people in order to make a record, or do a decent live show, and they asked Anders Fridén and Björn Gelotte to join the band, on vocals and drums, and they accepted. IN FLAMES were for the first time a band with a real line up.