The International Conference Kliment’s days 2023 (KD2023) is a notable event held from 9-11 November 2023 in Sofia, Bulgaria. The annual scientific conference is organised by the Faculty of Biology, Sofia University “St. Kliment Ohridski”. KD2023 served as a platform for the exchange of knowledge, sharing experiences, and fostering collaboration on innovative approaches within the fields of Biodiversity and Biological Education, Molecular Biology and Biotechnology, and Ecology and Sustainable Development. The conference featured a plenary session during which esteemed speakers present the following plenary lectures:• Boris Kryštufek, Slovenian Museum of Natural History, Ljubljana, Slovenia, Back to the future: reemergence of natural history.• Ariola Bacu, Department of Biotechnology, Faculty of Natural Sciences, University of Tirana, Albania, Biological indicators & single-cell cytotoxicity sensing - lessons learned on the quality of waters.• Adele Muscolo, Department of Agraria, “Mediterranean” University, Reggio Calabria, Italy, Fertilizer produced with wastes modulates antioxidant compounds and activities in tomato.• Ioannis P. Gerothanassis, Section of Organic Chemistry & Biochemistry, Department of Chemistry, University of Ioannina, Greece, Ligand-observed NMR: principles and applications in the field of biocatalysed reactions, ligand-macromolecular interactions and investigations at the cellular level.• Miodrag Stojkovic, SPEBO Medical, Leskovac, Serbia, Human pluripotent stem cells – a unique tool to decipher specific cell responses, diseases, and biomarkers.• Antoaneta Trendafilova, Institute of Organic Chemistry with Centre of Phytochemistry, Bulgarian Academy of Sciences, Sofia, Bulgaria, Secondary metabolites in Inula species from the Bulgarian flora and biotechnological approaches for their accumulation (as part of the Satellite Scientific Symposium “Medicinal and Aromatic Plants for Innovative Bioactive Products - MAPBIO”).A total of 148 participants actively engaged in KD2023, which included the parallel Satellite Scientific Symposium (MAPBIO). In addition to the plenary lectures, the conference featured 16 oral presentations delivered by a diverse group comprising four foreign authors, twelve Bulgarian authors, including five young scientists and PhD students. During the poster session, over 112 poster presentations were presented with over 200 participants, encompassing 15 foreign authors and 76 young scientists, students and PhD students. Additional information about the KD2023, including program, book of abstracts, etc. can be found on the official website of the conference: https://www.biofac.info.The successful execution of KD2023 was made possible through the support of the University Science Fund, as well as the dedicated efforts of the scientific and organizing committee. The active involvement of student volunteers in the event, along with the contributions of all third parties, played a crucial role in ensuring the event’s success.We are delighted to note the widespread resonance of the event within the scientific community, drawing participants from a diverse range of countries, including Albania, Slovenia, Greece, Italy, the Republic of Kosovo, the Republic of North Macedonia, Serbia, Türkiye, etc. The conference also attracted participants from various Universities and institutions in Bulgaria.The use of the Morressier platform facilitated a seamless reviewing process, showcasing the responsive collaboration between the editorial team, reviewers, participants, and the Morressier team.List of Editors, Conference Committee are available in this Pdf.