Bern 2000 was technical conference held in Bern, Switzerland. It gathered hundreds of people of various origins, affiliations and occupations, including the genius billionaire Tony Stark, the scientist Maya Hansen, the founder of A.I.M. Aldrich Killian and the surgeon Ho Yinsen. During the conference, Stark gave a lecture about integrated circuits, all the while being intoxicated.
During the conference, Stark met with other attendants like Yinsen and Wu, but most importantly met and flirted with Hansen. The two partied together after the lectures, waiting for New Year to come, and Stark suggested to Hansen that they go to her hotel room so they could review her work. Once in the elevator, and despite Happy Hogan trying to interfere, the couple was approached by Killian, who wanted to associate with Stark. As they had reached their floor, Stark told Killian to wait for him on the roof to discuss a potential collaboration.
However, Stark never made it to the roof to meet Killian. Instead, he remained in Hansen's room to discuss her research in Extremis and they slept together that night, leaving Killian alone on the roof to watch the fireworks for New Years Day. The humiliation he received from Stark during Bern 2000 deeply affected Killian, who grew a desire to exact revenge and developed a philosophy of anonymity, which would result in a war in the years to come.
Years later when both Yinsen and Stark were held captive by the Ten Rings, Yinsen reminded Stark that they had met during Bern 2000. Stark claimed he did not remember it, which Yinsen perfectly understood since he was heavily drunk at the time.