This week, Nature publishes retractions of two high-profile papers that claimed a major advance in the field of stem cells (see page 112). Between them, the two papers seemed to demonstrate that a physical perturbation could do what had previously been achieved only by genetic manipulation: transform adult cells into pluripotent stem cells able to differentiate into almost any other cell type. The acronym STAP (stimulus-triggered acquisition of pluri­potency) became instantly famous. 
 
 Soon after the papers were published on 30 January, cracks appeared in the edifice. As various media outlets including Nature’s independent news team reported, errors were found in the figures, parts of the methods descriptions were found to be plagiarized and early attempts to replicate the work failed. 
 
 The problems that initially emerged did not fundamentally undermine the papers’ conclusions. Moreover, replication of such work is not necessarily straightforward or quick, and the ability to use some techniques can be very sensitive to aspects of the experimental protocol. 
 
 Nevertheless, the RIKEN research centre in Japan, one of the institutions in which most of the work was carried out, promptly organized an inquiry and found inadequacies in data management, record-keeping and oversight (see go.nature.com/2vrjxs). One author was found guilty of misconduct — a charge that RIKEN reaffirmed following an appeal (see go.nature.com/tnxuhy). 
 
 We at Nature have considered what lessons we can derive from these flaws. When figures often involve many panels, panels duplicated between figures may, in practice, be impossible for journals to police routinely without disproportionate editorial effort. By contrast, image manipulation is easier to detect. Our policies have always discouraged inappropriate manipulation. However, our approach to policing it was never to do more than to check a small proportion of accepted papers. We are now reviewing our practices to increase such checking greatly, and we will announce our policies when the review is completed. 
 
 But only since the RIKEN investigation has it become clear that data that were an essential part of the authors’ claims had been misrepresented. Figures that were described as representing different cells and different embryos were in fact describing the same cells and the same embryos. 
 
 All co-authors of both papers have finally concluded that they cannot stand behind the papers, and have decided to retract them. 
 
 The papers themselves have now been clearly watermarked to highlight their retracted status, but will remain hosted on Nature’s website, as is consistent with our retraction policy. (In our opinion, to take down retracted papers from journal websites amounts to an attempt to rewrite history, and makes life needlessly difficult for those wishing to learn from such episodes.) 
 
 “We at Nature have considered what lessons we can derive from these flaws.” 
 
 We at Nature have examined the reports about the two papers from our referees and our own editorial records. Before publishing, we had checked that the results had been independently replicated in the laboratories of the co-authors, and we regret that we did not capture the authors’ assurances in the author-contributions statements. 
 
 We have concluded that we and the referees could not have detected the problems that fatally undermined the papers. The referees’ rigorous reports quite rightly took on trust what was presented in the papers. 
 
 For more than two years, Nature has been publishing articles that highlight the problems that can arise in the analysis and publication of the results of biomedical research. We have also launched several initiatives to improve our own rigour. For a collection of relevant content, see go.nature.com/huhbyr. 
 
 Underlying these issues, often, is sloppiness, whether in the handling of data, in their analysis, or in the inadequate keeping of laboratory notes. As a result, the conclusions of such papers can seem misleadingly robust. Another contributory factor lies in selection bias behind the data presented, whether implicit because the experiment was not randomized or blinded, or explicit in the deliberate selection of data that, usually with honest good intentions, are judged to be representative. (This is not to say that randomizing and blinding is always required, but more is needed than currently occurs.) 
 
 A manifestation of these problems has been a growth in the number of corrections reported in journals in recent years. It is hoped that the extension of our methods sections, the addition of a checklist intended to improve the standards of reporting, and our use of statistical advisers will reduce these problems in Nature. 
 
 In short: although editors and referees could not have detected the fatal faults in this work, the episode has further highlighted flaws in Nature’s procedures and in the procedures of institutions that publish with us. We — research funders, research practitioners, institutions and journals — need to put quality assurance and laboratory professionalism ever higher on our agendas, to ensure that the money entrusted by governments is not squandered, and that citizens’ trust in science is not betrayed. ||||| 
 
 April photo of scientist Haruko Obokata. (EPA/KIMIMASA MAYAMA) 
 
 On January 28, a young scientist known for her intelligence and ambition arrived at Japan’s renowned research institute Riken. Expected to deliver remarks about her groundbreaking research on the development of stem cells in mice, she was triumphant. “There were many days when I wanted to give up on my research and cried all night,” the 30-year-old Haruko Obokata said while addressing a phalanx of cameras at the news conference. “But I encouraged myself to hold on just for one more day.” 
 
 On Wednesday, she again arrived at Riken’s offices, but this time under very different circumstances. Her co-author had disavowed the two major scientific papers. Riken investigators said she “fabricated” or misrepresented her research. And the lauded scientific publication Nature that published the paper retracted it and is reviewing its method of vetting submissions. So, expression austere, she rushed past 50 reporters waiting outside Riken and disappeared into the laboratory to try and salvage what remained of her career, the Japan News says. 
 
 Under video surveillance, she will attempt to recreate the widely-trumpeted findings that allegedly showed stem cells could be made quickly by dripping blood cells into acid. Called STAP — “stimulus-triggered acquisition of pluripotency” — the discovery originally blew everyone away. The research purported to establish a new way to grow tissue and treat complicated illnesses such as diabetes and Parkinson’s disease with a simple lab procedure. Many called it the third most significant breakthrough in stem cell research. 
 
 That was then. Now Obokata, who denies misconduct and contends the STAP condition does exist, is suspected of duping two of the world’s leading scientific bodies. And on Wednesday, she and the other scientists conceded their studies were flawed and retracted them. 
 
 “We apologize for the mistakes,” the scientists wrote in the retraction, citing several “critical errors.” “These multiple errors impair the credibility of the study as a whole and we are unable to say without doubt whether the STAP-SC phenomenon is real. Ongoing studies are investigating this phenomenon afresh, but given the extensive nature of the errors currently found, we consider it appropriate to retract both papers.” 
 
 Nature as well says it has “considered” what lessons it can draw from retraction. In its statement, it concluded it “could not have detected the problems that fatally undermined the papers.” That said, it plans to amend some of its policies to better discern “image manipulation … Our policies have always discouraged inappropriate manipulation. However, our approach to policing it was never to do more than to check a small proportion of accepted papers. We are now reviewing our practices to increase such checking greatly.” 
 
 Problems with Obokata’s research emerged almost immediately. Something seemed off with some of the images in the study, and its language bore too great of a resemblance to another study published a decade before, according to the New York Times. 
 
 “As various media outlets including Nature’s independent news team reported, errors were found in the figures, parts of the methods descriptions were found to be plagiarized and early attempts to replicate the work failed,” Nature said. 
 
 That initial skepticism gave way to Riken’s own investigation. Its head soon concluded that the problems didn’t just constitute errors – but outright misconduct. The paper, he said, “amounts to phony research or fabrication.” 
 
 “Dr Obokata’s actions and sloppy data management lead us to the conclusion that she sorely lacks, not only a sense of research ethics, but also integrity and humility as a scientific researcher,” the investigative committee said, according to the Guardian. 
 
 Obokata, who has reportedly fallen into “ill health,” appealed the investigation’s results. But on May 7, Riken confirmed its initial investigation, accusing her of “fabrication” and “misconduct.” “Problems regarding the handling of the image data under investigation go beyond sloppy management,” the report found. 
 
 Weeks later, her co-author on the work recanted, saying the cells purportedly used in the study did not appear to be STAP cells after all. “There is no proof as to the existence of STAP cells,” Teruhiko Wakayama said at a news conference. “All the results of the analysis are moving toward denying the existence of STAP cells but I cannot say that the cells absolutely do not exist.” 
 
 Obokata is expected to work at Riken for the next five months to prove that they do. An interim report on her progress is expected in late July. 
 
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– A few months ago, Haruko Obokata appeared to be one of Japan's most promising young scientists. Her mind-blowing research on stem cells in mice, which apparently showed the cells could be made swiftly by dripping blood cells into acid, had just been published in the coveted scientific journal Nature. Yesterday, however, after her co-author renounced the pair's two major scientific papers on STAP—"stimulus-triggered acquisition of pluripotency"—Obokata finally admitted her research was flawed, the Washington Post reports. And though she's been accused of fabrication, a lack of ethics, and "sloppy data management," she denies any misconduct. "Multiple errors impair the credibility of the study as a whole," she and other scientists said in a retraction, noting "we are unable to say without doubt whether the STAP-SC phenomenon is real." She will, however, spend the next five months at Japan's research institute Riken trying to recreate her findings under video surveillance. Nature has also since retracted the studies after "errors were found in the figures, parts of the methods descriptions were found to be plagiarized and early attempts to replicate the work failed." The publication says it will now reconsider how it vets its studies, though it "could not have detected the problems that fatally undermined the papers."