Emotional availability (EA) is a relational construct that encompasses the ability of a dyad to share an emotionally connected, safe relationship. EA is operationalized by the multidimensional framework, which includes the observational EA Scales, the observational emotional attachment zones (EA-Z), as well as the EA Self-Report (EA-SR). The observational EA Scales measure the mutual interactive influences a child and parent may have on one another through observation of their affect and behavior and consist of 4 adult dimensions (sensitivity, structuring, nonintrusiveness, and nonhostility) and 2 child dimensions (responsiveness and involvement of the adult). The EA-Z refers to “emotional attachment styles” and is based on the summary of the observational EA Scales, assigned separately to adult and child (Emotionally Available, Complicated, Detached, Problematic/Disturbed/Traumatized or Traumatizing), with the potential that the emotional attachment perspective of the adult and child may not be the same. The EA-SR is about parental perceptions rather than observations, which should be taken into account in interpreting its findings. Collectively, these different measurements are referred to as the EA System. In this review, we focus on the EA-SR at any age, as well as EA observations, in the earliest months and adolescence.