As regards the issue of complexity, human brain is one of the most complex systems we know. The study of neural networks, their relation to the operation of single neurons and other important topics do and will profit a lot from complex systems approaches. As regards quantum physics, there can be no reasonable doubt that quantum events occur and are efficacious in the brain as elsewhere in the material world – including biological systems. This paper is intended to present an exhaustive viewpoint regarding the main actual hypothesis in what concerns human brain mechanisms of structuring and functioning.