Success stories of citizen science projects widely demonstrate the value of this open science paradigm and encourage organizations to shift towards new ways of doing research. While benefits for researchers are clear, outcomes for individuals participating in these projects are not easy to assess. The wide spectrum of volunteers collaborating in citizen science projects greatly contributes to the difficulty in the evaluation of the projects' outcomes. Given the strong links between many citizen science projects and education, in this work we present an experience with hundreds of students (aged 15–18) of two different countries who participate in a project on cell biology research — Cell Spotting — as part of their regular classroom activities. Apart from introducing the project and resources involved, we aim to provide an overview of the benefits of integrating citizen science in the context of formal science education and of what teachers and students may obtain from it. In this case, besides helping students to consolidate and apply theoretical concepts included in the school curriculum, some other types of informal learning have also been observed such as the feeling of playing a key role, which contributed to an increase of students' motivation.

Since 2009 Vetenskap & Allmänhet (Public & Science, VA) coordinates an annual mass experiment as part of ForskarFredag — the Swedish events on the European Researchers' Night. Through the experiments, thousands of Swedish students from preschool to upper secondary school have contributed to the development of scientific knowledge on, for example, the acoustic environment in classrooms, children's and adolescents' perception of hazardous environments and the development of autumn leaves in deciduous trees. The aim is to stimulate scientific literacy and an interest in science while generating scientific output. The essay discusses how the mass experiments can contribute to encouraging scientific citizenship.

Citizen science is one of the most dramatic developments in science communication in the last generation. But analyses of citizen science, of what it means for science and especially for science communication, have just begun to appear. Articles in this first of two special issues of JCOM address three intertwined concerns in this emerging field: The motivation of citizen science participants, the relationship of citizen science with education, and the implications of participation for creation of democratic engagement in science-linked issues. Ultimately these articles contribute to answering the core question: What does citizen science mean?

Citizen science has proven useful in advancing scientific research, but participant learning outcomes are not often assessed. This case study describes the implementation and tailoring of an in-depth assessment of the educational impact of two citizen science projects in an undergraduate, general education course. Mixed-methods assessment of citizen science within a college classroom demonstrates that public participation in scientific research can positively alter attitudes towards science. The timing and type of assessments yielded significantly different results and qualitative assessment provided depth and context. However, disentangling the impact of the course from participation in the projects is the biggest challenge.

Many citizen science projects deal with high attrition rates. The Dutch Great Influenza Survey is an exception to this rule. In the current study, we conducted an online questionnaire (N=1610) to investigate the motivation and learning impact of this loyal, active participant base. Results show that the desire to contribute to a larger (scientific) goal is the most important motivator for all types of participants and that availability of scientific information and data are important for learning. We suggest similar projects seek (social) media attention regularly, linking project findings to current events and including the importance of participants' contribution.

Whereas the evolution of snow cover across forested mountain watersheds is difficult to predict or model accurately, the presence or absence of snow cover is easily observable and these observations contribute to improved snow models. We engaged citizen scientists to collect observations of the timing of distributed snow disappearance over three snow seasons across the Pacific Northwest, U.S.A. . The primary goal of the project was to build a more spatially robust dataset documenting the influence of forest cover on the timing of snow disappearance, and public outreach was a secondary goal. Each year's effort utilized a different strategy, building on the lessons of the previous year. We began by soliciting our professional networks to contribute observations via electronic or paper forms, moved to a public outreach effort to collect geotagged photographs, and finally settled on close collaboration with an outdoor science school that was well-positioned to collect the needed data. Whereas the outreach efforts garnered abundant enthusiasm and publicity, the resulting datasets were sparse. In contrast, direct collaboration with an outdoor science school that was already sending students to make weekly snow observations proved fruitful in both data collection and educational outreach. From a data collection standpoint, the shift to an educational collaboration was successful because it essentially traded wide spatial coverage combined with sparse temporal coverage for dense temporal coverage at a single, but important location. From a public engagement standpoint, the partnership allowed for more intensive participation by more people and enhanced the science curriculum at the collaborating school.

The design, delivery and evaluation of JCOM Masterclasses has given us the opportunity to reflect on the audiences, training needs and training schemes available to people working at different levels and in different contexts to communicate STEM subjects to a diverse variety of people. Although not always widely available, short courses in the communication of science have been offered in a number of countries around the world over the past few years. We felt it is now time to open a discussion on the rationale, the methods and the objectives of such training programmes.

A hybrid combination of art and science is used to communicate science in a primary school setting. The purpose of the work is to enhance student awareness of the science behind understanding the global climate system with a focus on the cryosphere. An experiment in communicating science is conducted by taking the collaborative experiences of a professional artist and scientist, which are then combined and projected onto an ostensibly everyday primary school classroom project. The tangible end result is a stand-alone contemporary art work that then is the focal point of community-based promotion of the science and creativity involved. A range of qualitative evaluation elements suggest that the approach does improve student engagement with the scientific approach and reduces the student's uncertainty about ``what science is''.

Open Science may become the next scientific revolution, but still lingers in a pre-paradigmatic phase, characterised by the lack of established definitions and domains. Certainly, Open Science requires a new vision of the way to produce and share scientific knowledge, as well as new skills. Therefore, education plays a crucial role in supporting this cultural change along the path of science. This is the basic principle inspiring the collection of essays published in this issue of JCOM, which deals with many subjects ranging from open access to the public engagement in scientific research, from open data to the social function of preprint servers for the physicians' community. These are issues that go along with the targets of the FOSTER project (Facilitate Open Science Training for European Research) funded by the European Union, which has provided interesting food for thought in order to write this commentary.

For decades, particle physicists have been using open access archives of preprints, i.e. research papers shared before the submission to peer reviewed journals. With the shift to digital archives, this model has proved to be attractive to other disciplines: but can it be exported? In particle physics, archives do not only represent the medium of choice for the circulation of scientific knowledge, but they are central places to build a sense of belonging and to define one's role within the community.