In “U Don’t Know” Jay-Z explains his monetary success in both the drug and rap games. Providing the blueprint for the marriage of soul-sampling and heavy bass, it is recognized as one of his best tracks.
Produced by Just Blaze, the track samples “I’m Not to Blame” by Bobby Byrd. Just has said that he was never fully satisfied with the beat, hence his 2002 remix:
We did The Blueprint in such a short period of time that we knew we had to get it out right away. Not that I rushed through ‘U Don’t Know.’ We knew it was hot, but I wanted to do more with it … the remix [is] the same beat but it’s smashing you in your face so much harder that it really brings the whole thing home. So, its the same dynamic of starting something, but then really revisiting it later on and luckily I was able to.
According to Jay, the track came about as the result of a beat-making battle between Just and Kanye:
During that time, I had two rooms in Baseline. It was a big room that I was in, that I’d record in. Then it was a small room that Just would be in doing beats. What happened was, Just would peep his head in and hear what me and Kanye was doing and would just go back mad … It was like this every day. It was like a heavyweight slugfest. For three days they was just knocking each other out. And I remember him playing that joint, and I was like, ‘Oh my God!’
Jadakiss stated that he originally had the instrumental to this song before Jay-Z but he didn’t know what to do with it and expressed regret that he was not able to make a song out of it. This most likely has to do with him being impressed with what Jay did to it.