From January to December 2019, over 150 people from 13 countries engaged in a yearlong social experiment called Living in a New Republic of the Heart. Together our group made a radical commitment to learn to "be the change" that could catalyze the whole-systems transformation necessary to navigate humanity's extreme civilizational crisis. That's a lofty intention. We knew we could only hope to succeed incompletely. But we would publish the results, and whatever we learned-both successes and failures-would be useful input for other groups attempting to be living laboratories of holistic transformation. We foresaw that a new field of inquiry was spontaneously emerging and that our experiment represented both an exemplar and an advancement of it. We call this new field "Intentional Cultural Evolution." People all over the world are seeking to awaken together, to cooperate in new ways that involve new depths of friendship, new agreements, new practices. Whole-systems transformation will require entirely new ways of being human, individually and together. We saw that this important new field will not advance primarily via abstract academic research, but rather via action-inquiry-learning by doing, iterating, and rapidly evolving best practices. Our experiment and this book seek to contribute to this field in two ways: (1) By "being the change" ourselves-learning by doing; and (2) by sharing what we learn. This volume reports our best practices and learnings in a format designed to be useful to others. We deeply hope it may inspire and inform your own experiments in intentional cultural evolution.