In 2007, a highly publicized paper was published in the first tier scientific journal, Nature Biotechnology. The authors described the derivation of amniotic fluid-derived stem (AFS) cells. The authors presented evidence that AFS cells differentiate into several cell types, including neurons. The impact of these claims was far reaching since AFS cells could be a resource for cell therapy without the ethical challenges of using embryonic stem cellsⁱ. In particular, cell therapy for neurodegenerative diseases such as Parkinson's disease and Huntington's disease require a source of transplantable neurons (Isacson 2003). Now correspondence has been published by the same journal, which questions the robustness of the experimental findings presented (Toselli et al. 2008). This important decision by the editors of Nature Biotechnology to publish correspondence that challenges high impact findings strengthens the basis of stem cell research. Indeed, discourse is an essential part of the scientific progress (Hwang et al. 2005, Kennedy 2006). The correspondence by Toselli et al. draws upon their experience and specifically addresses multiple aspects of the description of neuronal differentiationⁱ by AFS cells. We hope that De Coppi et al. are able to address the concerns raised and provide further evidence in support of their initial claims.