This book gathers selected papers that were submitted to the 2021 International Conference on Comprehensible Science (ICCS 2021) that aims to make available the discussion and the publication of papers on all aspects of single and multi-disciplinary research on conference topics. ICCS 2021 held on June 18-19, 2021. An important characteristic feature of conference is the short publication time and worldwide distribution. Written by respected researchers, the book covers a range of innovative topics related to: artificial intelligence research; big data and data mining; blockchain and cryptocurrency; business, finance and accounting and statistics; cyber security systems; ecology systems; educational technologies; engineering and technology; innovative economics; media technologies; medicine, public health and rehabilitation; nutrition and diet researches; physical and material sciences; and smart cities and contracts. This book may be used for private and professional non-commercial research and classroom use (e.g., sharing the contribution by mail or in hard copy form with research colleagues for their professional non-commercial research and classroom use); for use in presentations or handouts for any level students, researchers, etc.; and for the further development of authors' scientific career (e.g., by citing and attaching contributions to job or grant application).