「我觉得女孩子与女孩子之间有一种很重要的感情，那是没有语言可以形容的，跟男朋友再好也没法达到。」- 李心洁 /xinhuanet/

I'm not a boy so I don't know, but I guess the kind of intimacy between two girls is not what can be found between two boys, be it friendship or romance. There seems to be a particular, different form of chemistry. Again, I'm not a boy so I don't know, but I guess mother-daughter relationship is different from father-son relationship in a similar way. Is this type of relation character natural, or formed by norm? Both, it must be. But I wonder how different (or similar) they can be, if the society hasn't formed so clear a set of attributes for each sex.