The book of the famous German physicist, biologist, popularizer of science offers the reader 365 experiments that will expand deepen the basic knowledge of the natural science cycle of school subjects about the world and natural phenomena. Experiments do not require preliminary preparation. The description of each experiment includes a list of materials, detailed instructions, the intended result and an explanation of the observed phenomenon. Some experiments are supplemented with cognitive texts that reveal the observed phenomena in more detail. For experiments, simple, safe and affordable materials are used, which are in almost every home.