Listening to Dr. Hansen, both Luke and Tony got strange expressions on their faces.
By the time she was done, Luke had already been staring at the tycoon with a complicated expression for a long while. He finally said, "Hm… this is why you need to be a decent person."
Tony's expression changed, and he cursed several seconds later. "F*ck you!"
As for who the "you" referred to, that was a matter of opinion.
What made them react this way was Dr. Hansen's explanation of Killian's love-hate relationship with Tony.
It was 1999 in Bern, Switzerland, on Christmas Eve. Tony slept with Dr. Hansen, and also took a look at her research project – Project Extremis.
Using dendritic cells to recode the human body could allow a person to " regrow" missing parts, like a plant.
After sleeping with Dr. Hansen, Tony casually wrote down an equation after a flash of inspiration, solved a key problem with Project Extremis, and left.