<Tr> <Td_colspan="7"> The interns of Seattle Grace Hospital start to use every free minute to study for their upcoming exam which will determine their entire residency in the surgical field . Cristina is jealous of George who can study with Callie, whose learning cards have become legendary . After the realization that George and Izzie might have feelings for each other, Callie decides to give the cards to Cristina . The attending physicians vie for the Chief position by tending to the chairman of the hospital board, after he is admitted as a patient . They soon learn that there is a fish in his urinary tract and learn that his wife has been aware of his affair with his secretary . She eventually resigns and leaves him, and his wife asks for divorce . In the clinic, Izzie treats a patient with a recurring cold, which turns out to be a symptom of something worse . Webber starts to question his decision to retire as he believes that there is a lot more he can do as a surgeon and cannot be done with his career in his early fifties . Cristina gets annoyed at Burke as he tries pressuring her into choosing a flavor for their wedding cake while she is trying to study . Addison and Alex deliver Ava's baby, through a cesarian - section, before sleeping together, but afterwards Alex tells her to make sure that it never happens again . Derek starts to question his relationship with Meredith, feeling that he is the only one putting an effort for it to work out . George tells Izzie that he is considering transferring to a different hospital . </Td> </Tr> <Tr> <Th> 58 59 </Th> <Td> 22 23 </Td> <Td> "The Other Side of This Life" </Td> <Td> Michael Grossman </Td> <Td> Shonda Rhimes </Td> <Td> May 3, 2007 (2007 - 05 - 03) </Td> <Td> 21.23 </Td> </Tr> <Tr> <Td_colspan="7"> After things become too complicated in Seattle, Addison travels to Los Angeles to reunite with her old friends from Columbia University College of Physicians and Surgeons . Much to her best friend's shock, the real reason for her visit is in order to get pregnant but she is devastated to learn that she cannot . Whilst there, Addison assists her friend in treating a surrogate mother, who had sex with three different men who all claim that the baby is theirs . Cristina finds difficulty in planning her wedding under the constant watch of her and Burke's mother, who are determined to create an extravagant wedding, despite her wishes of having a small ceremony . Callie is surprised to be invited to be Cristina's bridesmaid . Susan is admitted to the hospital, bringing Thatcher with her, but he suspects that she might be trying to bring Thatcher and Meredith together by faking hiccups . Mark talks to Derek and expresses his disappointment in not working things out with Addison, who he had truly fallen in love with . Burke is surprised when his mother tells him that he's making a mistake marrying Cristina, but she reassures him that she supports his decision . George is determined to transfer to Mercy West, despite Izzie's continuous begging . Addison becomes the temporary obstetrician - gynecologist at the Oceanside Wellness Center in Los Angeles and deals with the aftermath of the discovery that she cannot have children . She is comforted by Pete Wilder who flirts with and eventually kisses her . The doctors offer her a position, but she denies it after realizing that Seattle is where her life is . The Los Angeles team also continue to treat a man with no sex drive, which infuriates his wife, who has a high one . After Susan returns to the hospital with chest pain, she is rushed into emergency surgery and ultimately dies . Thatcher is devastated by the news and blames Meredith for her death, and slaps her . George and Burke confide in each other about their relationship problems, and Burke's intensify after an argument with his mother . Izzie finds difficulty in accepting that George is going to transfer because of her, but realizes that she can't deny her feelings towards him, which leads to them kissing . Meanwhile, Derek must perform surgery on Ava and she gets her hopes high after realizing that she might get her memory back . </Td> </Tr> <Tr> <Th> 60 </Th> <Td> 24 </Td> <Td> "Testing 1 - 2 - 3" </Td> <Td> Christopher Misiano </Td> <Td> Allan Heinberg </Td> <Td> May 10, 2007 (2007 - 05 - 10) </Td> <Td> 19.58 </Td> </Tr>

When did meredith and derek get back together