Solid ball like feeling things in breasts?

I have noticed through feeling my breasts here and there that I have these like solid, ball-like feeling things inside my breasts. I have noticed that I've had them for many years but I was just wondering if this is a normal part of the breast or if I should get it checked with my doctor? Do you other ladies have the same thing? I'm not too to worried cause there's no pain or anything but just curious in cause it may be something serious.