## 1 Introduction  
Social, political, and technological pressure towards intelligent systems able to help and support humans in any non-trivial process and activity is leading the way for new programming paradigms, providing suitable abstractions and mechanisms for modelling and designing complex software systems. More the twenty years of academic research on multi-agent systems (MAS) have promoted agent-oriented models and technologies as the most suitable candidates for the design and development of distributed and intelligent applications in complex and dynamic environments. To actually become \"the next big thing\", however, MAS need to complete their transition from a (mostly) academic product to the industry mainstream. To this end, a huge number of aspects and issues relating to MAS techniques and methods have to be scrutinised and explored within the many relevant application scenarios where complex intelligent systems are required: this is one of the main motivations behind the special issue. Before delving into the individual contributions gathered, a few general statistics and observations are useful to have an overview of the content and outreach of this special issue:  
* 55 papers have been submitted for peer review, out of which 17 were finally published, resulting in an acceptance rate of \(\approx\)31%
* the median article processing time to publish, intended as the time passed from submission to online availability, is 40 days, with a standard deviation of \(\approx\)17 days--dates are publicly available on the special issue web page ([[https://www.mdpi.com/journal/applsci/special_issues/Multi-Agent_Systems](https://www.mdpi.com/journal/applsci/special_issues/Multi-Agent_Systems)]([https://www.mdpi.com/journal/applsci/special_issues/Multi-Agent_Systems](https://www.mdpi.com/journal/applsci/special_issues/Multi-Agent_Systems)))* papers generated an average of 0.76 citations (1.71 standard deviation) and \(\approx\)687 downloads (\(\approx\)326 standard deviation) per year--citations, downloads, and also views count are publicly available on each paper own web page, accessible starting from the special issue one
* published papers have been co-authored by authors coming from 13 countries, covering Europe, Asia, and South America. Among these, Spain is the most represented, having 5 papers with at least one local author  
When considering that this is the first year of the special issue, and that Applied Sciences is relatively new to the field of research in agent-oriented models and technologies, we are very happy with both the number of submissions and their quality, as well as with the number and quality of the papers finally published. After their publication, papers are typically valued by the number of citations they get; obviously, they need a bit more time than less than a year to start generating mentions. Nevertheless, some of the papers published here have already started gaining attention. Figure 1 shows the wordcloud generated from the full pdfs of the published papers. Unsurprisingly, the most mentioned word is \"agent\", followed by \"model\" and \"user\". The latter one may have a quite generic meaning, thus is difficult to interpretate, but the second one already highlights one of the relevant areas of application of MAS, that is, agent and multi-agent based modelling--which is one of the four main topics emerging from the analysis of the content of the published papers.