What are the possible conflicts between children and parents?

Children and parents are different planets in our Solar System. They are two generations of the time. That is why they have a lot of reasons to conflict. It may be their habits, tastes, thoughts, school rate and others. It is too dangerous when they can not solve their problems without crying, quarrel and manhandling. I think that each side should be more patient, valid and wise. That time parents will think that they have best children and children be happy to have such good parents. They could be even friends.