Julien Delpierre @JulienDelpierre@qoto.org

The great success of the AlphaFold programs poses the following questions: (i) What is the main reason for this success? (ii) What exactly do AlphaFolds do: prediction of the 3D protein structure based on its amino acid sequence and knowledge of the protein physics or recognition of this 3D structure, based on the similarity between some parts of its amino acid sequence and parts of sequences with already known 3D structures? The answers given in this paper are: The main reason for the tremendous success of the AlphaFold is (i) the usage of huge protein databases, which already cover all or almost all of the protein superfamilies existing in nature; (ii) using these databases and the resulting multiple sequence alignments and coevolutionary information (like correlations in pairs and especially in triplets of amino acid residues in the contacting chain regions), AlphaFold recognizes a 3D structure of the examined amino acid sequence by a similarity of this sequence (or its parts) to related sequences with already known 3D structures. Concluding, I have to emphasize that this paper does not diminish the merit and utility of AlphaFold; it only explains the basis of its success. ### Competing Interest Statement The authors have declared no competing interest.

A web graph network originally constructed in 2003 as a testbed for information-retrieval techniques, including web search engines. Distributed by University of Glasgow.

The last few years have seen the number of preprints in our field grow exponentially. More and more of us are posting preprints and coming to appreciate the benefits of preprinting. As authors, it gives us control over when we make our findings public. As readers, we're able to discover exciting findings in our field sooner than would be the case if the paper was only made accessible after the traditional peer-review and publishing process. Overall, it's clear that preprints are becoming an important feature of how we communicate our science, and they are also having a major impact on the way we think about scientific publishing.At Development, we've been preprint enthusiasts for many years. As editors, if we see a preprint that we think might be suitable for Development we'll write to the authors to invite them to submit their work for our consideration. We also encourage authors to post preprints, whether this is on bioRxiv or other preprint servers, and have simplified the process of co-submitting manuscripts to Development and bioRxiv (via direct portals in our submission systems). Not surprisingly, we've seen a steady increase in the number of authors using these routes; last year, approximately 20% of submitted articles were posted on bioRxiv via these portals (compared with just 8% in 2017) and, more broadly, just over 35% of articles published in Development were preprinted prior to formal publication.But, we realise that the growth in preprints brings new challenges. It is becoming increasingly difficult to keep up with the latest preprints in the field and to assess the importance and validity of studies outside our area of expertise. We have therefore been working on several ways to guide readers to relevant preprints. We post monthly lists of developmental and stem cell biology preprints on our online community site, the Node (https://thenode.biologists.com/monthly-preprint-list/). If there are any we've missed, please do let us know. Together with our publisher, The Company of Biologists, we are also involved in preLights (https://prelights.biologists.com/) – a community-run online resource that features short summaries of notable preprints. These are selected and written by an international group of early career researchers (‘preLighters’) who summarise and comment on the preprints they find most noteworthy. This initiative is helping to build interest in preprints and is assisting researchers as they try to navigate and digest the ever-growing preprint literature. Since its inception, nearly 1250 preLights have been posted and the site has received over 500,000 views. Moreover, we have recently begun to highlight some of these preLights in the journal's Table of Contents. We also participate in ASAPbio's ‘Preprint Reviewer Recruitment Network’ (https://asapbio.org/preprint-reviewer-recruitment-network). This scheme is a way for researchers to gain experience in peer-reviewing preprints and it also provides journals and editors with potential new reviewers to call on.Now, in this issue of Development, we are further extending our efforts to support the use of preprints by introducing a new article type – ‘In preprints’. Each ‘In preprints’ article will offer a summary of a recently posted preprint, or small number of related preprints, and provide some analysis of the work and put it into broader context. We're aiming for each article to be a succinct commentary that we hope readers will find useful and that will encourage further reading of the preprint or related work. Our intention is that our ‘In preprints’ feature becomes another way in which readers are guided to the preprints that matter the most to the field. We also hope they will encourage discussion and debate of the latest findings within our community.In line with our initiatives to support early career researchers (Briscoe and Grewal, 2021), we are encouraging more established investigators to team up with early career researchers to write ‘In preprints’ articles. We are particularly keen to see partnerships between researchers that haven't previously worked together, as we hope this will foster new interactions and discussions within a field. You can see the first ‘In preprints’ article in this issue of Development (Lowell and Blin, 2022), but keep your eye out for more in the future. If you are interested in writing an ‘In preprints’ piece, even if you don't yet have a preprint or writing partner in mind, do please get in touch.As preprints become an increasingly routine part of our scientific landscape, we hope you find ‘In preprints’ a useful and convenient way to stay on top of the latest research in the field. As always, we're interested in hearing from you, whether you have feedback on our existing preprint initiatives or suggestions for new ones, or if you simply want to tell us about how preprints have affected your research.