Since 1940s the ideas and understanding of autism have changed a great deal. Until 1960s autism was mainly understood within the psychoanalytic framework: it was explained as disturbed ego differentiation due to lack of mother’s emotional availability. Currently autism is understood as a diverse neurobiological disorder with strong genetic influences. Major shifts have taken place in the classifications and diagnostic manuals of the disorder. In the latest, fifth, edition of Diagnostic and Statistical Manual for Mental Disorders (DSM-5) the previously separate subcategories of the autism spectrum, including Asperger syndrome, are not used any more and are assembled under the broad term autism spectrum disorder (ASD) with three severity levels. The prevalence of ASD is estimated to be about 1–1.5% and it has increased markedly in recent decades, mainly due to the broader diagnostic criteria, changes in reporting practices, and increased awareness of ASD. The ASD has a very strong genetic component, however, there is no single ASD-causing gene, and the clinical heterogeneity of ASD reflects the genetic diversity of the disorder. There is no universal cognitive theory to explain the symptomatology of ASD. Numerous ongoing studies aim to identify the diferent etiopathogenetic subtypes of ASD. Improvement in and support of the quality of life of individuals with ASD are of the greatest importance.