Founded in 1996, Frontiers in Bioscience-Landmark celebrated its 25th Anniversary of continuous publication in 2021. Starting from that year, the journal moved to a fully open access gold format. It was my privilege to assume the role of Editor-in-Chief at that time, and to act as Editor for this Special Issue entitled “Twenty-five years at the frontiers of knowledge: a quarter-century of ‘Frontiers in Bioscience’”. This 25th Anniversary celebratory collection of 22 papers from a wide range of biological science disciplines perfectly illustrates the broad appeal of the Journal as a publication vehicle to disseminate the latest findings in diverse fields. These papers cover a wide range of studies on different species, from insects to amphibians, fish, pigs, rats and humans, originating from many different countries (the US, the UK, Spain, Australia, Italy, China, Korea, Germany, Canada, France etc, but also from low and medium income countries such as Lebanon and Bangladesh). Of the 22 papers, half are original research on highly diverse topics including a detailed analysis of signaling pathways in insect heart development [1], stress management in breast cancer patients [2], regulation of myelopoiesis in zebrafish [3], an analysis of heat shock protein expression in human glioblastomas [4], a new method for screening for human topoisomerase inhibitors using genetically-modified yeast [5], genetic influences on systemic iron levels in humans [6], transcriptomics studies on frog development [7], clinical studies on malnourished children with diarrhoea [8], a theoretical investigation of approaches to characterizing logic operations in model neurons, synapses, and neural circuits [9], the effects of methionine-restricted diets on the growth of pigs [10], and the effects of iron on kidney disease in rats [11]. The other half of the papers are reviews on an equally diverse range of topics, including drugs for Alzheimer’s Disease [12], spheroid cell cultures [13], bioactive polyphenols [14], ribosome evolution [15], purinergic signaling in bone cancer [16], spontaneous regressions in cancer [17], genetic analyses of pituitary cancers [18], pharmacological chaperones [19], drug targeting for SARS-CoV-2 infection [20], calcium signaling in mesenchymal stem cells [21], and relationships between the control of circadian rhythm and neurodegeneration [22]. We sincerely thank all authors and readers for their interest in the Journal and look forward to the next 25 years of exciting advances in the biological sciences and an expanded role for the Journal in the OA publishing landscape.