The Sun Earth Connection Coronal and Heliospheric Investigation (SECCHI) on the NASA Solar Terrestrial Relations Observatory ( STEREO) mission is a suite of remote sensing instruments consisting of an extreme ultraviolet imager, two white light coronagraphs, and a heliospheric imager. Two spacecraft with identical instrumentation will obtain simultaneous observations from viewpoints of increasing separation in the ecliptic plane. In support of the STEREO mission objectives, SECCHI will observe coronal mass ejections from their birth at the Sun, through the outer corona, to their impact at Earth. The SECCHI program includes a coordinated effort to develope magneto-hydrodynamic models and visualization tools to interpret the images that will be obtained from the two spacecraft viewpoints. The resulting three-dimensional analysis of CMEs will help to resolve some of the fundamental outstanding questions in solar physics.