gender transition
Gender transitioning is the act of using hormones to slowly change your body to match the sex characteristics of the gender you identify as. For example, trans women take estrogen to feminize themselves, causing feminine characteristics to become more prominent such as larger breasts.
This is not to be confused with Gender Transformation, which is a tag that implies immediate shifting of genders. Gender transitioning is a slow process with the best results being visible a few years after starting treatment.