回複：請教過來人關於Postdoc offer的寶貴經驗。。。

You should get Professor's invitation letter first and then you will receive a DS2019, it will take around 3 weeks, during that time, you will be asked to provid all of your informations, such as copies of your degree, diploma and passport et al, all of these will probaly be done online. Don't worry, just wait, when you get your DS2019, you can go to the US consulate with offer letter, your passport and all other documents, usually people will be checked for security clearance and this will take around 3-4 weeks depends on which Country you are. Good luck!