  Coronal mass ejections (CMEs) are spectacular ejections of material from the
Sun as seen in the coronal field of view. Regular observations are possible
with both ground-based and space-based coronagraphs. I present our current
understanding of CMEs based on multi-wavelength observations from groundbased
instruments as well as from space missions such as SoHO. Based on the
continuous and multi-wavelength observations of CMEs from SoHO over a period of
more than a solar cycle, the physical properties of CMEs are described. Recent
observations of CMEs with the SECCHI coronagraphs, namely COR1 and COR2 aboard
the twin STEREO spacecrafts A and B are also presented. STEREO surpasses
previous missions by providing a 3-D view of CME structure from two vantage
points. Applications of STEREO observations to 3-D reconstructions of the
leading edge of CMEs are described.
