A major challenge for teacher education in the twenty-first century is to provide society with qualified teachers to teach and prepare the next generation of citizens. The situation in, for example, Sweden and South Africa faces huge issues concerning an increased lack of teachers in the future, as well as difficulties with teacher attrition. Examples from the USA show that up to 50% of new teachers quit working as teachers within 5 years. The difficulties with knowledge transfer to new generations, are a global threat. In this chapter, the deficiency of examined teachers is addressed in Section 1. This is followed by an overview of two key aspects of teachers' professional development, namely bridging the gap between practice and theory to enhance teaching quality as well as the importance of practice-based professional development to maintain teachers to work as teacher in a long-term perspective. The results of a case study of students' views on theories are presented, showing a strong experienced dichotomy between theory and practice, and difficulties to see how theories could be used to better understand classroom situations. Finally, a proposal of how to bridge the gap between theory and practice with designed modules is presented.