Your child now knows whether he/she is a boy or a girl. He will also try to put things in categories. For instance, boys play with cars while girls play with dolls. You may also find him playing more with same-sex peers rather than opposite sex-peers.
What you need to know
Try to encourage friendship with children of the opposite sex. This is something to be nurtured and your little one will value the friendship as he may not do this at school.