This chapter provides an introduction to the book by providing a basic understanding of suicidal behavior. It first provides the reader a general knowledge of the epidemiological, clinical, and behavioral presentations of suicidal behaviors. In many situations, acts of nonfatal suicidal behavior will precede lethal suicidal behavior, and a suicidal process with clear implications for prevention is commonly found. The multiple causes of suicidal behaviors will be discussed, and it will become clear that each suicide results from a complex convergence of many possible sociocultural and neurobiological (e.g. genetic) factors. In spite of the unique characteristics of each suicide in terms of personal features and social circumstances, many such suicides can be understood as the consequence of an interaction between stressors and a specific vulnerability to suicidal behavior. Stressors may include problems in relational, professional, or financial areas, or consequences of psychiatric disorders such as depression that may precipitate suicidal behavior in vulnerable individuals. It is particularly with regard to this vulnerability that neuroscience studies have contributed substantially to our insights, and thus provide opportunities for prevention and treatment.