The gender gap in Science, Technology, Engineering and Mathematics (STEM) has drawn the attention of research and academic communities due to its impact in the Digital Society, targeting the fourth and fifth 2030 sustainable development goals of achieving quality education and gender equality. Recent studies show that women are enrolling STEM studies in smaller proportion than men and that they have a larger probability to renounce to their jobs or to take leaves. In this scenario, the involvement of educational institutions is seminal to change this trend. The School of Engineering of the University of Valencia (ETSE-UV), Spain, launched in 2011 a pilot program to promote STEM careers, focusing on increasing and retaining the number of female students choosing these studies. Building from this experience, the Girls4STEM project has been launched in 2019 with the aim of reaching female students from 6 to 18 years old, their families and teachers. In this paper, we present and motivate the project's objectives and main activities, framing them in current state of the art's literature. Preliminary results of the pilot program actions are presented, demonstrating the statistically significant impact on the percentage of enrolled female students and motivating the subsequent Girls4STEM project.