  Coronal mass ejections (CMEs) are associated with the eruption of magnetic
flux ropes (MFRs), which usually appear as hot channels in active regions and
coronal cavities in quiet-Sun regions. CMEs often exhibit the classical
three-part structure in the lower corona when imaged with white-light
coronagraphs, including the bright front, dark cavity, and bright core. The
bright core and dark cavity have been regarded as the erupted prominence and
MFR, respectively, for several decades. However, recent studies clearly
demonstrated that both the prominence and hot-channel MFR can be observed as
the CME core. The current research presents a three-part CME resulted from the
eruption of a coronal prominence cavity on 2010 October 7 with observations
from two vantage perspectives, i.e., edge-on from the Earth and face-on from
the Solar Terrestrial Relations Observatory (STEREO). Our observations
illustrates two important results: (1) For the first time, the erupting coronal
cavity is recorded as a channel-like structure in the extreme-ultraviolet
passband, analogous to the hot-channel morphology, and is dubbed as warm
channel; (2) Both the prominence and warm-channel MFR (coronal cavity) in the
extreme-ultraviolet passbands evolve into the CME core in the white-light
coronagraphs of STEREO-A. The results support that we are walking toward a
unified explanation for the three-part structure of CMEs, in which both
prominences and MFRs (hot or warm channels) are responsible for the bright
core.
