As widely acknowledged, Merleau-Ponty highlighted the reciprocal relationship between empirical (including scientific) and philosophical (or transcendental) explorations of the world. Remarkably, he also attributed this sense of circularity to Husserl. To deepen our understanding of this relationship, this presentation examines Merleau-Ponty’s engagement with a set of ideas discussed by Husserl in the Crisis (§§ 59-60) and related manuscripts (Hua XXIX) in connection with the concept of “streaming in” (einströmen). Husserl recognised that scientific truths and theoretical practices not only refer back to the lifeworld as their foundation but also “flow back into” it, thus expanding it. While contemporary commentators occasionally discuss this concept, James Dodd (2004) emphasises it as a central yet still neglected notion in Husserl’s transcendental philosophy. On the one hand, Merleau-Ponty echoes Husserl’s view that cultural constructions have meaning only for a subject who experiences “intuitively” a universal horizon of the Lebenswelt, and in contrast to it. However, Merleau-Ponty cites the concept of “streaming in” in Phenomenology of Perception to support his well-known argument about the “impossibility of a complete reduction.” Later, he references it to challenge the strict division between “natural” and “constructed” aspects of the world. My aim in this presentation is to first explain how Merleau-Ponty conceives the mechanisms by which our constructions—especially linguistic, theoretical, and scientific—relate to the lifeworld; and second, to articulate in what sense the concept of Lebenswelt remains philosophically valuable, even if we accept that it paradoxically includes the representations we construct of it. I begin by providing an overview of Husserl’s use of the notion of einströmen and its contemporary interpretations. Building on this foundation, I will explore how, in his late manuscripts, Merleau-Ponty adopts and transforms the idea of “streaming in” through concepts such as “brute world” and “brute Being,” and how it leads him to redefine the relationship between the “natural” and “cultural” worlds.