It should be noted, however, that large pectoral muscles themselves will not make breasts increase in cup size, because the bra holds the fat and glandular tissue of the breast, not the muscle (muscle increase in the chest, however, may increase the band number part of the bra size, which is more representative the size of one's chest overall rather than just the fleshy mounds which protrude from it.) In fact, a large increase in muscle mass (in general, not on the chest specifically) will often lead to smaller breasts because as the lean muscle-to-fat ratio changes, the overall fat percentage is likely to drop, causing breast shrinkage (i.e., the more fat you have the bigger the breasts, and vice versa, though that isn't the *only* factor involved.)

Breasts may also be made to look larger by such clothing choices as empire waist shirts or dresses, low-cut clothes when paired with a bra that allows for/creates cleavage, a lack of bra with a tight shirt or developing more svelte abs. If there's a specific individual who you want to impress by appearing to have large(r) breasts, sticking them in their face often works, too.