The pectoral minor runs underneath your pec from I believe your 2nd rib to your 5rd rib near the outside of your pec. If you make it larger it will push the outer pec outwards more... If your pectoral minor gets excessively strong, and you dont have a good strong back, and stretch the hell out of your pecs, the over powering nature of this muscle will pull your delts forward and will potentially create tendon impingments in your shoulder...
To really hammer this mucle group do limited ROM pullovers... I do these every week on chest day and the outsides of my pecs have really pushed themselves out...
DON'T FORGET TO STRETCH YOUR PECS IF YOU PLAN ON GROWING YOUR PECTORAL MINOR!