Сonsciousness is what most people believe they have. This term is hard to define. In 17th Rene Decartes claimed that consciousness consists of spiritual and physical substances. Now this theory is famous as decartes dualism. However, critics of that time, Baruch Spinosa in particular, pointed out that this distinction showed the great problem of brain and reasoning interaction By the 1690 John Locke had defined consciousness as "perception of the things happening in a human's mind". In the middle of the 19th century scientists began to solve the mystery of consciousness. In the 1860 Wilhelm Wundt tried to prove that consciousness is caused by physiological processes and highlighted the necessity of understanding qualia, i.e subjective experience. In 1929, an Austrian psychiatrist Hans Berger made the first discovery by defining a method for detecting the electrical activity of the brain, called an electroencephalogram. The discoveries of Berger started the research on neuron corellation of consciousness - types of activities of brain connected with conscious experience. Nowadays they form the main target of research and scientists think it can follow the understanding of how our brain joins a big number of neuron corellates of consciousness into a unity. Another experiment was committed in 1960s. The skin of a patient was insignificantly irritated. The patient felt nothing, but her brain still appeared to react on the simulation To prove this fact helps the discovery made in 1960s: our conscienceis only a small part of all brain activity. Scientists affected people’s skin, EEG showed that brain fixed irritation, but the patients said that theydo not feel anything. Huge number of questions arise but whether one organism has consciousness or not is not valid. More correct question is the level of consciousness of different organisms. Such sophisticated structure of consciousness makes finding answers even more harder.