Hescheler has been working with embryonic stem cells ever since the late 1980s. Beginning with studies on cellular signal transduction, and starting with works on signalling pathways in different cells (g-protein phosphorylation, electrophysiology of channels) he focussed on embryonic stem cells and has since defined many important basic aspects of both fundamental research and clinical applications. He was the first scientist worldwide to perform electrophysiological and functional experiments on stem cells and differentiated phenotypes thereof. He achieved a first functional characterization of cardiomyocytes developed from embryonic stem cells which is an important prerequisite for their subsequent use in regenerative medicine. He thus pioneered the establishment of stem cell research for application in transplantation medicine. In 2002, he was among the first scientists in Germany to obtain permission to work with human embryonic stem cells. In his current position, as Chairman and Director to the Institute for Neurophysiology at the University of Cologne, his research areas include work on embryonic and adult stem cells, induced pluripotent stem cells, mesenchymal stem cells and germline pluripotent stem cells. Among progressing the use of stem cells for translational purposes, aiming at tapping the potential of stem cell biology towards clinical application, Hescheler actively promotes the vision of EPAA through innovative alternative testing strategies, applying stem cells towards toxicity testing. Apart from the rationale of promoting 3R principles it is his goal that coordinating a multidisciplinary research effort undertaken by various projects and consortia led by Hescheler will generate pathway- and evidence-based understanding of long-term toxic effects, thus moving toxicology from a rather descriptive science towards a more mechanistic-driven predictive one.