Sex is the state of being male or female. According to Monique Wittig, “sex is natural and also social”. Sex is not just physical and anatomical differences such as differences of sex organs, the amount of hormones, particular characteristics and body shapes between men and women. At first, how do people recognize them either men or women? From their body functions? or From tehir feeling about themselves? People generally suppose to decide their sex by genitalia, when babies are born. However,the concept of sex which is human beings have either male or female is constructed by society. Sex is connected a concept of femininity and masculinity. So, when babies are born, we connect vagina with girl, and also we connect penis with boy. Because people recognize genitals as either girl or boy, they socially choose and decide their sex. When people can not identify their genitalia as either female or male, they can not recognize them as human beings. If we don’t have sex, aren’t we human beings?