when you became an expert, you would be able to know...

where would most probably the bugs, when you just had a glance at the program~

which bunch of nerve you have to anesthetize, when you are about to do a surgical operation~

what engine is being used in a car, when you just listen to its sound~

how many gearwheels does it has inside a watch, when you just listen to a "tick" of it~

what would a man gonna do, when you just look at his eyes once~