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.
Composition of blood. The blood is composed of cells, cell fragments and an aqueous solution (plasma). Blood makes up about 8% of the human body weight. It contains erythrocytes, leucocytes, thrombocytes (platelets) and plasma. The volume percentage of all blood cells in the whole blood is about 45% in adults (hematocrit). The rest consists of liquid plasma (e.g. water, plasma proteins, electrolytes etc.). Recommended video: Circulatory system