Artificial Intelligence has become nowadays one of the main relevant technologies that is driven us to a new revolution, a change in society, just as well as other human inventions, such as navigation, steam machines, or electricity did in our past. There are several ways in which AI might be developed, and the European Union has chosen a path, a way to transit through this revolution, in which Artificial Intelligence will be a tool at the service of Humanity.

The present regular issue consists of 10 works with a great variety of topics. It begins with two interesting health-related works: the first one, reviews different approaches that can help fight COVID-19 and the second one, tries to solve an optimal control problem of cancer treatment using an artificial neural network. It continues with algorithms that can help in industrial processes such as reducing the temperature of electronic circuits or carrying out chromium layer thickness forecast.

In this special issue, we want to gather some innovative applications that are currently pushing forward the research on Blockchain technologies. In particular, we are interested also in those applications that put the focus on the data, enabling new processes that are able to leverage relevant knowledge from the data. This special issue will be successful if readers gain a better understanding on how Blockchain can be applied to very diverse areas, and might even be interested in designing, implementing and deploying an innovative solution to a completely different field of knowledge.