Introduction
![The top papers on reproduction research 2004|[ndash]|2008](/nm/journal/v14/n11/images/nm1108-1178-I1.jpg)
Rather than relying solely on citations, we posed these questions directly to a large group of leaders in reproductive biology and medicine, asking them to identify what they perceived as the most important papers in their respective fields over the past three to four years. We received feedback from nearly 40 experts, and their responses were incredibly varied—much more than what we found in our previous issues on tuberculosis or metabolic disease—no doubt reflecting the diverse expertise of the scientists we polled. The list of papers suggested by at least three experts, along with some illuminating comments, is presented below. The numbers in blue show the percentage of respondents who picked that paper.
Topping the list are two papers that could not be more different: on the one hand, the discovery that natural killer cells regulate developmental processes at the site of implantation and, on the other, the production of tissue-engineered follicles that produce live offspring.
![The top papers on reproduction research 2004|[ndash]|2008](/nm/journal/v14/n11/images/nm1108-1178-I2.jpg)
Perusing the whole list, several broad themes emerged as having seen important advances: the immunology of reproduction, the pathophysiology of preeclampsia, the effect of environmental toxins on reproduction and the intricate relationship between germ cells and stem cells. In the pages that follow, experts in each field discuss the key papers that advanced these and other areas (shaded in yellow) in a series of News and Views articles. The remaining papers from the list (shaded in blue) are discussed in brief on pages 1192–1193. And to find out how much resemblance this list bears to a list of high-impact papers generated by more traditional means (citations), turn to page 1180.
![The top papers on reproduction research 2004|[ndash]|2008](/nm/journal/v14/n11/images/nm1108-1178-I3.jpg)
![The top papers on reproduction research 2004|[ndash]|2008](/nm/journal/v14/n11/images/nm1108-1178-I4.jpg)

