Machine Learning (ML) is rapidly changing the world, having an increasingly important role in many areas of everyday life. Entire industries, like healthcare, manufacturing and automotive have been completely revolutionized by the huge impact that research is having in the Artificial Intelligence (AI) field. Data plays an important role in this revolution: the enormous amount of data collected, together with the rise of new technologies to process them, brought to the development of new ML techniques. Nevertheless, many of them still face issues that slow down their adoption. One of the most important is presented by their increasing complexity causing a lack of trust in their decisions and outputs.