Both, actually. Everyone in my family is born with the skills needed to summon those elements. Learning to control it, however, is something all the children are trained for. It's our primary lessons.

We're expected to know how to summon and manipulate it upon our fifth birthday.

There are children that can do it and others that need more training or never had the talent to do it in the first place.

[Now, where Nike lies in the scale between talent and hard work, it falls upon the latter than former.]