Cells—> Tissues—> Organs—> Systems—> Organism.
The same type of cells which carry out a specific function are organised into a tissue. For examples, a group of muscle cells form a muscle tissue while a group of nerve cells form a nerve tissue. They are organised to work together to perform specific functions as the result of cells in the human body do not work individually.
An organ is a group of tissue that cooperates to carry out a specific life process. For examples, a group of muscle tissues, epithelial tissues and connective tissues form blood vessels. Several organs are organised into a system. Each system consist of several organs which are organised to carry out life processes such as respiration, reproduction and digestion.
Various systems in the human body are well organised to carry out all the life processes efficiently. They are able to function because the cellular components work together to ensure the survival of human beings.
The human brain is well developed to integrate information's and store them as memory. This allows human beings to have the ability to talk, think rationally, create new things, learn from experience and use languages. The ability to do all these makes us really special compared to other organism.