In the biological context there are many different parts of the human body however all of these parts can generally be broken down into a cell form. The single cell of the human is the smallest part of life itself. The cell is considered a living organism because it can reproduce, needs oxygen to survive as well as fuels. The human cell can also be referred to as the building block of life. The general human cell is around one nanogram in weight and cannot be seen by the human eye.
The human cell was discovered with absolute proof of existence as early as 1839 when a scientist discovered what he though was moving matter in skin tissue samples through a microscope. It was not until much later that the cell was broken down into all its parts because of the need for more powerful microscopes and other scientific tools.
All organisms are generally either single cell organisms or are made of multiple cells to make a larger structured organism. When a woman is impregnated her egg changes structure and becomes a single cell which continues to split and grow into a fetus then child and then into a fully grown human being. Throughout this process many cells are destroyed while others replace them and this is all a part of growing and staying healthy. Our bodies are made up of billions cells with thousands of different kinds of cells.