Although for the majority of the series Booth and Brennan denied that their relationship was anything more than friendly professionalism, they admitted to Dr. Sweets that they kissed and nearly spent the night together after their very first case together. After this discussion, Booth attempted to convince Brennan to give a relationship a try. However, she declined, telling him that she, unlike him, is not a gambler, and is n't able to take that kind of a chance. They have subsequently attempted to date other people, although the fact that Booth once comments that he regards Brennan as his "standard '' for other women suggests that he, at least, has not completely moved on. Brennan does admit to her best friend Angela Montenegro that as time has gone on, she is unsure if she wants to keep doing consulting work for the FBI, citing that she is tired of murderers and victims, and is constantly worried that something will happen to Booth and she will be unable to save him. In the climax of Season Five, Brennan and Booth part ways for a year -- he goes to Afghanistan while she leaves for the Maluku Islands in Indonesia -- but they promise to meet, one year from that day, at the Lincoln Memorial.
when do booth and brennan have their first real kiss
after their very first case together