In this family masterclass, participants will learn how modern nuclear reactors work and will build their own 3D model. A nuclear reactor is a highly complex structure, but the basic principles of its operation can be understood by anyone interested in physics. This engaging masterclass is designed for schoolchildren and their parents. First, the instructor will explain the structure of modern reactors, the first radioactive loop, and the concept of a "loop." After the theoretical part, participants will conduct hands-on experiments demonstrating various effects and scientific phenomena that underlie the reactor's operation. In conclusion, each guest will assemble a model of the VVER-1000 reactor from parts printed on a 3D printer. Children aged 12 to 14 may participate only when accompanied by parents. Group gathering starts at 14:40 in the museum lobby, and at 14:55 everyone will be taken to the Laboratory where the session will take place. For more details, visit the official website. Photo provided by the organizer.