Gender is one of the most important categories, if not the most important category, in human social life. Though at first sight distinguishing between female and male may seem straightforward, a closer look readily reveals that this fundamental categorization is fairly complex—it is imbued with a host of cultural meanings and practices pervading each and every aspect of individual, interpersonal, group, and societal processes. Thus, all known cultures provide rich and well-differentiated sets of concepts and terms to categorize and characterize boys and girls, men and women, to separate between female and male roles, rights, and responsibilities. In all known cultures, females and males meet with distinct sets of gender-related beliefs and expectations exerting powerful, and often subtle, influence on their thoughts, feelings, and behaviors.