When you exercize your arms, the muscles get bigger. the more you exercize your left arm the bigger that muscle and all associated muscles get. in the same way your left breast will become bigger...
It's normal for teens as well as adults. All humans have one side of the body that is bigger than the other and just about all women have different sized breasts. It can be one hangs lower or just...
In one way that is like asking why clothes or garden tools, buildings, musical instruments, cars, trucks, planes, ships, etc. have different shapes and sizes... The reason is because the diverse uses...