This school, addressed to PhD students and postdocs in both theoretical and observational cosmology, will introduce the fundamental physical processes for the study of reionization and the first stars, and the cosmological epoch that can be observed via 21-cm absorption and emission. A variety of observational probes are available for the study of the Universe when density fluctuations first became non-linear at the smallest scales at which baryons were able to collapse. The evolution of perturbations when the atomic medium was illuminated by the first ultraviolet radiation from stars, starting heating and reionization, offers unique observational probes in absorption and emission for observations in the 21-cm line in radio observatories, and in Lyman alpha and other atomic lines in optical observatories. This can have many cosmological applications for constraining the composition and initial conditions that were created in the early Universe. This course will introduce and explore the tools that are essential for leading researchers in this area. The course will consist of two daily lectures during 4 days with ample time for questions and discussions, as well as time for openly discussing special problems and present research with the invited lecturers. Students will be able to present poster papers about their research, and there will be time to discuss them among lecturers and participants. The poster papers can be on more general topics in cosmology than the subject of the course. All students are welcome to present poster papers, and are asked to submit an abstract of their poster on this website to do so.