Lew has developed a reputation as a details guy, who regularly logs in 16-hour days at the White House. He observes the Jewish Sabbath of leaving work before sundown on Friday and abstaining from work on Saturdays. However, he is known to have worked Saturdays in urgent situations.
One detail about Lew that came to light this week is his loopy, illegible signature, which will grace the lower right-hand side of each new dollar bill if he's confirmed as Treasury Secretary. Obama joked about his nominee's penmanship at Thursday's press conference, saying Lew "assures me that he is going to work to make at least one letter legible in order not to debase our currency."
CNNMoney's James O'Toole contributed reporting.