The Sun's atmosphere is a highly structured but dynamic place, dominated by the solar magnetic field. Hot charged gas (plasma) is trapped on lines of magnetic force that can snap like an elastic band, propelling giant clouds of material out into space. A range of ground-based and space-based solar telescopes observe these eruptions, particularly the new STEREO space probes that can track an eruption from the Sun all the way to the Earth. (Contains 11 figures and 8 online resources.)