Context: In 1974, Humberto Maturana and Francisco Varela published De Máquinas y Seres Vivos. Autopoiesis: La organización de lo vivo in Santiago, Chile as a little book. A second edition of this publication was proposed in 1994, and the present document is a recent translation of Maturana's reflections "twenty years after." Problem: The book clearly enunciates what it means to say that living systems are molecular autopoietic systems, and this Preface reflects on the shift of understanding from earlier notions of self-referred or auto-referred systems to the concept of autopoiesis. Implications: The Preface describes the systemic quality that is human living and human sense-making. It marks what we can retrospectively see as the bridge between the explicitly biological studies of Maturana (and Varela), and the later, more anthropological and therapeutic work of Maturana with Gerda Verden-Zöller between 1989 and 1994 and, especially, with Ximena Dávila Yáñez since the year 1999. Results: The underlying understanding implicit in this document outlines in great clarity the implications of Maturana's fundamental insights. It presents both a logical and passionately argued case for mutual respect, grounded in scientific findings in biology. The Preface is a clear vision of why Maturana's work has been so influential for reflexivity and constructivism.