Both nature (genetics) and nurture (environment) affect who we are as individuals.
We are given certain qualities at birth over which we have limited control and these shape us in countless ways. This, of course, is not the whole picture, as our experiences and our responses to them mold us also. In general, our genetic predispositions are either expressed or repressed based upon the environments in which we reside. A computer metaphor helps here: We have a hard drive (nature) but we can add, subtract or modify numerous types of software (nurture) that we choose to introduce to our operating systems.