Fear is an emotion that is particularly important to human and animal existence. It is a reaction to threatening events and is elicited when self-preservation goals are posed in danger during the pursuit of actions directed at other goals. A common view of fear in the neuroscience literature is that fear triggers the "fight or flight" response, characterised by increased heart rate, breathing, and muscle tension, which allows the individual to escape from danger or defend itself against a predator or non-specific. Based on the presence or absence of a stimulus, the brain regulates the strength and duration of this apparent coping mechanism. When this regulatory system malfunctions, however, it can lead to excessive fearfulness in certain individuals. Excessively fearful individuals appear to have difficulty suppressing the body's response to stress. This book examines the various aspects of this interesting emotion.