On their way through the solar system, solar wind streams and coronal mass ejections encounter a variety of different obstacles, which are presented in overview in this chapter. These obstacles—smallest dust particles, meteorides, asteroids and comets, planets, and moons—differ significantly with respect to their sizes, properties as well as distances from the Sun. When the solar wind encounters magnetized obstacles, it first senses their magnetic field, compresses it on the solar side, and creates a bow shock wave in front of it. The solar wind flows around such obstacles laterally and, by folding its magnetic fields, causes the formation of elongated magnetic tails on the side facing away from the Sun. In contrast, non-magnetized rock-like obstacles, on whose hard surface hardly any ionized plasma matter can form, are flowed around by the solar wind comparatively undisturbed and calmly.