Man is like an individual who tries to be separated without being isolated, at least this is the perspective from which Donald Woods Winnicott starts to describe the psychological development of the child from birth, who, ultimately, in his adult life, will be the result of his primary interactions with the people he loves and hates, at the same time; Added to this, other aspects appear that are closely related for Winnicott to the environment of the first years. For him, before sexuality there was helplessness... and dependence comes before good or evil. Vulnerability and transitional phenomena would constitute a good part of his proposals as a pediatrician and psychoanalyst, even in epistemological opposition to several of the approaches of Freudian psychoanalysis, not out of stubbornness, not out of simple disagreement, but rather due to the result of his meticulous efforts. observations and contrasts based on the formulation of hypotheses, which he managed to develop with rigorous discipline. Winnicott's explanations about vulnerability, dependence and transitionality focus on an important proposal for clinical intervention. This article shows what could be the form of a scheme of this psychoanalyst's thinking about transitional phenomena in particular, and the discovery of some psychopathological structures closely related to transitionality.