This special edition presents a snapshot from around the world of the current state of the research devoted to the issues of professional development of teachers. Teachers' professional and pedagogical activity is significantly changing today. In many respects, these changes are explained by a new understanding of the purpose and result of education, which is formulated in the documents of educational reform in Russia and in the world, in the context of achieving a new quality of mass education. The question that becomes extremely important is: "How exactly should the teacher's professional and pedagogical activity change in order to provide a new quality of education meeting the "challenges of the time?". These issues are described in the works of the leading Russian and foreign researchers in the field of teacher education who participated in the Fifth International Forum on Teacher Education held on 29-31 May, 2019 in Kazan Federal University (IFTE-2019) (http://ifte.kpfu.ru/en/home-page/). Researchers share their views and research results on the issues of modernization and development of the content of teacher education. They discuss questions related to values and priorities within the field of modern teacher education, to modernization processes and contents of teacher education including the requirements of a competency-based approach. Key issues of teachers' professional development within this and other essential topics related to teacher education are also touched upon in 16 papers included into this book. The authors of the papers issue represent a variety of positions and address a number of the questions raised in the high quality debate. The evidence they present emanates from different nations and different universities.