From September 16 to 19, 2024, an international symposium to celebrate the centennial of the discovery of the gastrula organizer by Hans Spemann and Hilde Mangold, was held at the University of Freiburg, Germany, where they studied embryology. There were 41 plenary lectures, 11 short talks, and 182 poster presentations, with more than 300 participants from 23 countries. The symposium covered research topics broadly related to developmental, cell, genome, and evolutionary biology, mainly focused on early animal development. In addition to in vivo studies on topics such as gastrulation, embryonic patterning, cell polarity, and morphogenesis, recent studies using gastruloids and organoids, which recapitulate embryogenesis and organogenesis in in vitro cell culture, were also presented at this symposium, entitled Self-Organization in Biology. Most of the reported studies used vertebrate models such as mice, frogs, and zebrafish
however, evolutionary studies involving invertebrate and plant models were also presented. Presentations employing traditional methods such as cell transplantation and phenotype screening, and state-of-the-art technologies such as single-cell omics, high-resolution imaging, and computational analysis showed that experimental embryology has a long history, to which studies of the organizer have contributed significantly. Here we discuss memorable aspects of the symposium in the hope that this report will encourage young scientists to actively participate in face-to-face international conferences.