The difficulty of conducting research in the field of developmental psychology is a cross-cutting theme of this book. The author examines a number of basic laws and principles that must be taken into account when conducting your own research and evaluating third-party research. This publication has three main goals. The first of them is to help develop the skills necessary to qualitatively study various phenomena in developmental psychology, in connection with which principles and instructions of different roles are presented, some of which relate directly to developmental issues, while others relate to psychology in general. The second goal is to familiarize readers with the most important areas of scientific work in this area. The third goal is to develop not only the skills to critically evaluate any research, but also the ability to draw adequate conclusions based on it. This book is addressed to everyone who wants to deepen their knowledge of problems and research methods in developmental psychology: students, graduate students, teachers of psychology departments, psychologists and psychotherapists .