The development process of the heart and cardiovascular system is fundamental in human development and highly regulated by genetic factors. This process needs to be highly regulated to prevent malformations. Nevertheless, some heart defects may be identified, especially with modern imaging methodology. Atrial septal defects (ASDs) are particularly common. Understanding the mechanisms involved in ASD formation is fundamental for developing new treatment strategies. In this article, we explore cardiac development and embryology, with a focus on atrial septal defects and their clinical implications.