The study of heliospheric space weather, especially in the Earth’s magnetosphere and ionosphere, is of great importance to mankind in this age of sophisticated technology and ambitious space projects. With the radiation bursts in solar flares, the magnetic eruptions on the Sun, and the fluctuations in the steadily flowing solar wind, the main contributors to space weather are presented. The resulting geomagnetic storms affect modern civilization and space travel. Among other things, they can interfere with telecommunications, destroy electrical components, and endanger the health of astronauts. Space weather prediction centres must therefore provide timely warnings of the hazards posed by solar and heliospheric processes. At the end of this chapter, findings of heliobiology are reported, which deals with the possible effects on human health.