First of all, you need to know whether the biting is really from aggression, or if it is over-excited playing. Puppies love to play, and part of the playing process is to bite. Whether that is because they want attention or a toy, or if it is because they are teething. The great thing is, it is pretty easy to spot actual aggression. If they are biting to play, they will have a fun demeanor about them, they will be bouncy, wagging their tail, panting through excitement, etc. Teething will be more like gnawing at things, and aggression will show a different side of your puppy.
While aggression in puppies is not completely unheard of, it is pretty rare. The thing that many people see as aggression is a continuation of their lives as smaller puppies, being with their litter. The way that litters interact is through play fighting, whether with each other or with their parents, or both. The difficulty that people face is how to train their puppies not to bite in the first place. We will save that for another article in the future, though!