This Research Topic eBook includes articles from Volume I and II of The Future of Physiology: 2020 and Beyond series: Research Topic “The Future of Physiology: 2020 and Beyond, Volume I” Research Topic “The Future of Physiology: 2020 and Beyond, Volume II” The term Physiology was introduced in the 16th century by Jean Francois Fernel to describe the study of the normal function of the body as opposed to pathology, the study of disease. Over the ensuing centuries, the concept of physiology has evolved and a central tenet that unites all the various sub-disciplines of physiology has emerged: the quest to understand how the various components of an organism from the sub-cellular and cellular domain to tissue and organ levels work together to maintain a steady state in the face of constantly changing and often hostile environmental conditions. It is only by understanding normal bodily function that the disruptions that leads to disease can be identified and corrected to restore the healthy state. During the summer of 2009, I was invited by Dr. Henry Markram, one of the founders of the “Frontiers In” series of academic journals, to serve as the Field Chief Editor and to launch a new Open-access physiology journal that would provide a forum for the free exchange of ideas and would also meet the challenge of integrating function from molecules to the intact organism. In considering the position, I needed to answer two questions: 1) What exactly is Open-access publishing?; and 2) What could Frontiers in Physiology add to the already crowded group of physiology related journals? As a reminder, the traditional model of academic publishing “is a process by which academic scholars provide material, reviewing, and editing expertise for publication, free of charge, then pay to publish their work” and, to add insult to injury, they and their colleagues must pay the publisher a fee (either directly or via an institutional subscription) to read their published work [slightly modified from the “The Devil’s Dictionary of Publishing” Physiology News (the quarterly newsletter of the Physiological Society) Spring 2019: Issue 114, page 8]. In the traditional model, the publisher, not the authors, owns the copyright such that the author must seek permission and may even be required to pay a fee to re-use their own material (such as figures) in other scholarly articles (reviews, book chapters, etc.). In contrast, individuals are never charged a fee to read articles published in open-access journals. Thus, scholars and interested laymen can freely access research results (that their tax dollars paid for!) even if their home institution does not have the resources to pay the often exorbitant subscription fees. Frontiers takes the open-access model one step further by allowing authors (rather than the publisher) to retain ownership (i.e., the copyright) of their intellectual property. Having satisfied the first question, I then considered whether a new physiology journal was necessary. At that point in time there were no open-access physiology journals, and further, many aspects of physiology were not covered in the existing journals. Frontiers afforded the unique opportunity to provide a home for more specialized sections under the general field journal, Frontiers in Physiology, with each section having an independent editor and editorial board. I therefore agreed to assume the duties of Field Chief Editor in November 2009. Frontiers in Physiology was launched in early 2010 and the first articles were published in April 2010. Since these initial publications, we have published over 10,000 articles and have become the most cited physiology journal. Clearly we must be fulfilling a critical need. Now that it has been over a decade since Frontiers in Physiology was launched, it is time to reflect upon what has been accomplished in the last decade and what questions and issues remain to be addressed. Therefore, it is the goal of this book to evaluate the progress made during the past decade and to look forward to the next. In particular, the major issues and expected developments in many of the physiology sub-disciplines will be explored in order to inspire and to inform readers and researchers in the field of physiology for the year 2020 and beyond. A brief summary of each chapter follows: In chapter 1, Billman provides a historical overview of the evolution of the concept of homeostasis. Homeostasis has become the central unifying concept of physiology and is defined as a self-regulating process by which a living organism can maintain internal stability while adjusting to changing external conditions. He emphasizes that homeostasis is not static and unvarying but, rather, it is a dynamic process that can change internal conditions as required to survive external challenges and can be said to be the very basis of life. He further discusses how the concept of homeostasis has important implications with regards to how best to understand physiology in intact organisms: the need for more holistic approaches to integrate and to translate this deluge of information obtained in vitro into a coherent understanding of function in vivo. In chapter 2, Aldana and Robeva explore the emerging concept of the holobiont: the idea that every individual is a complex ecosystem consisting of the host organism and its microbiota. They stress the need for multidisciplinary approaches both to investigate the symbiotic interactions between microbes and multicellular organisms and to understand how disruptions in this relationship contributes to disease. This concept is amplified in chapter 3 in which Pandol addresses the future of gastrointestinal physiology ,emphasizing advances that have been made by understanding the role that the gut microbiome plays in both health and in disease. Professor Head, in chapter 4, describes areas in the field of integrative physiology that remain to be examined, as well as the potential for genetic techniques to reveal physiological processes. The significant challenges of developmental physiology are enumerated by Burggren in chapter 5. In particular, he analyzes the effects of climate change (environmentally induced epigenetic modification) on phenotype expression. In chapter 6, Ivell and Annad-Ivell highlight the major differences between the reproductive system and other organ systems. They conclude that the current focus on molecular detail is impeding our understanding of the processes responsible for the function of the reproductive organs, echoing and amplifying the concepts raised in chapter 1. In chapter 7, Costa describes the role of both circadian and non-circadian biological “clocks” in health and disease, thereby providing additional examples of integrated physiological regulation. Coronel, in chapter 8, provides a brief history of the development of cardiac electrophysiology and then describes areas that require further investigation and includes tables that list specific questions that remain to be answered. In a similar manner, Reiser and Janssen (chapter 9) summarize some of the advancements made in striated muscle physiology during the last decade and then discuss likely trends for future research; to name a few examples, the contribution of gender differences in striated muscle function, the mechanisms responsible of age-related declines in muscle mass, and role of exosome-released extracellular vesicles in pathophysiology. Meininger and Hill describe the recent advances in vascular physiology (chapter 10) and highlight approaches that should facilitate our understanding of the vascular processes that maintain health (our old friend homeostasis) and how disruptions in these regulatory mechanisms lead to disease. They also stress the need for investigators to exercise ethical vigilance when they select journals to publish in and meetings to attend. They note that the proliferation of profit driven journals of dubious quality threatens the integrity of not only physiology but science in general. The pathophysiological consequences of diabetes mellitus are discussed in chapters 11 and 12. In chapter 11, Ecelbarger addresses the problem of diabetic nephropathy and indicates several areas that require additional research. In chapter 12, Sharma evaluates the role of oxidative damage in diabetic retinopathy, and then proposes that the interleukin-6-transsignaling pathway is a promising therapeutic target for the prevention of blindness in diabetic pateints. Bernardi, in chapter 13, after briefly reviewing the considerable progress that has been achieved in understanding mitochondrial function, lists the many questions that remain to be answered. In particular, he notes several areas for future investigation including (but not limited to) a more complete understanding of inner membrane permeability changes, the physiology of various cation channels, and the role of mitochondrial DNA in disease. In chapter 14, using Douglas Adam’s “The Hitchhikers Guide to the Universe” as a model, Bogdanova and Kaestner address the question why a young person should study red blood cell physiology and provide advice for early career scientists as they establish independent laboratories. They the, describe a few areas that merit further attention, not only related to red blood cell function, but also to understanding the basis for blood related disease, and the ways to increase blood supplies that are not dependent on blood donors. Finally, the last two chapters specifically focus on non-mammalian physiology. In chapter 15, Scanes asks the question, are birds simply feathered mammals, and then reviews several of the significant differences between birds and mammals, placing particular emphasis on differences in gastrointestinal, immune, and female reproductive systems. In the final chapter (chapter 16) Anton and co-workers stress that since some 95% of living animals species are invertebrates, invertebrate physiology can provide insights into the basic principles of animal physiology as well as how bodily function adapts to environmental changes. The future of Physiology is bright; there are many important and interesting unanswered questions that will require further investigation. All that is lacking is sufficient funding and a cadre of young scientists trained to integrate function from molecules to the intact organism. George E. Billman, Ph.D, FAHA, FHRS, FTPS Department of Physiology and Cell Biology The Ohio State University Columbus OH, United States