Each of us has felt afraid, but no one fully understands the origins of this feeling. It is summary of the most plausible versions of the biological essence of fear. Fears are caused by certain patterns of threat-related stimuli. Most types of categories such as fear and disgust are built by evolution process. Thus, due to this reason, it will be not possible to determine fear from the other emotions of an alien species without sufficient knowledge about the environment of their planet and the mechanisms for evolution on that planet.Fear is an intervening process between the context-dependent stimuli and behavior response based on reflexes and empirical experience. It is not assigned to the conscious feeling of being afraid or behaviors like screaming and running away. Rather, fear is a central state that in some way causes the conscious experience, fear behavior and calls some reflexes. In other words, fear is what links sets of stimuli to patterns of behaviors. In addition, unlike with reflexes, this link is much more flexible and the state can exist for some time after the eliciting stimuli. Definitions of fear and threat would be circular in case fears recognition is anchored only to stimuli, not behaviors. Hence, certain sets of stimuli and behaviors are attached; if they do not, we would never be able to differentiate fear from other emotional states of people or animals, but we can. Moreover, there are clinical distinguishing processes that are observed in the brain.As with emotional behavior in general, trait anxiety and anxiety disorders are considerably heritable. Furthermore, it is plausible that such disorders are caused by complex polygenic interactions with environmental stressors, rather than by any single gene. All in all, close to 20% of the population suffers from an anxiety disorder of some kind in any given year. Generalised anxiety disorder manifested in chronic worry about a chain of events, mostly attached to the future. On the other hand, panic disorder can result in a severe and intensive fear response. In addition, a panic attack can result in lack of ability to cope with the situation. Phobias consist of both predictive anxieties as well as intensive fight responses, often called by specific classes of stimuli. Such stimuli are called fear-inducing stimuli, that recall to fear-related thoughts and memories about a specific trauma. There is no separate single structure in the brain that is in charge of fears and not even a set of sufficient structures that can be easily researched. Fear evoked by different classes of stimuli that may be processed by partly separate neural systems. Furthermore, humans brain invoke consciousness to this process. What is more, people tend to do a poor job of identifying the source of their fears. Considering all the reasons it is hard to identify the origin of the fear disorders. There is no consequence among scientists, some argue that “fear” is a psychological construct involving cerebral cortex and fear cannot be applied to animals, others state that it is a biological pathology. Consequently, all the theories about the fear are based on non-perfect researches and partially consists of assumes.