The NASA satellite TRACE was the first mission to image an entire cycle of solar activity, studying the Sun at both its turbulent maximum and demure minimum. Specifically, it was used to examine the Sun's corona and the so-called transition region between the upper chromosphere and corona where temperatures rise rapidly. Launched on 2 April 1998, TRACE carried a telescope of 0.3-m aperture that imaged the motions of hot gas in the Sun's outer layers at a range of ultraviolet wavelengths. These gas motions are controlled by complex magnetic fields, and it is interactions in the magnetic fields that give rise to solar flares and large-scale mass ejections. The satellite observed some fine-scale structures for the first time as well, including coronal or solar moss, a sponge-like structure found at the base of some coronal loops. After 12 successful years in orbit and taking millions of images, TRACE took its last image on 21 June 2010.