Gender, the sense of being male or female, is well-established by the time children are

Gender, the sense of being male or female is well established by the time children are in pre-school at the age of 3-5 years. This is the age where children are usually eager to learn. They always want to touch, taste, smell see and test things for themselves. This is where they will notice differences in behavior and characteristics of people. That is why they will start to identify different genders around them.

The answer would be interphase.