The understanding of mental states is a fundamental element of most psychotherapies. We present in this work an original method named micro-analysis whose aim is to clarify the description and modelization of mental states in the context of psychoanalytic psychotherapies. This method improve the description of the phenomenological experience of the patient and can be considered as a focused free association process that improves the explicitation of subjective experience. After having described the main methodological elements relating to micro-analysis, which is itself part of a more global method called cognitive analysis, we present its use during psychoanalytic psychotherapies. The experience of the subject seems decondensed through this method which helps to catalyze symbolization processes. The micro-analysis thus improves the understanding of the subjective experience of the patient and represent a promising approach for modeling subjective experience between psychoanalytic models and cognitive neurosciences.