Oh? "The lab?" That's got his interest, and it seems to need a second look of Idia. "What do you do in there? --Building things?"

...which could fall under a few of the available spaces in the lab, but Tidus is definitely thinking something closer to machines than blacksmithing, like Q'uila does. Or maybe chemicals, but really, Tidus can't make a good guess just from looking at the guy.

(But, likely not blacksmithing.)