That's why I always recommend starting with a blog or website first. Create a content website on a very focused theme/niche. Build up traffic to that website through continuous, useful updates. Learn how to market the website, and as your following grows, then you'll have people to promote your social network to.
Human body. The human body is the entire structure of a human being. It is composed of many different types of cells that together create tissues and subsequently organ systems. They ensure homeostasis and the viability of the human body. It comprises a head, neck, trunk (which includes the thorax and abdomen), arms and hands, legs and feet.
Of course, the earth's crust is only the outer portion of the earth. Future research will tell us about the composition of the mantle and core. The most abundant element in the human body is oxygen, making up about 65% of the weight of each person.