  Magnetic flux ropes are characterized by coherently twisted magnetic field
lines, which are ubiquitous in magnetized plasmas. As the core structure of
various eruptive phenomena in the solar atmosphere, flux ropes hold the key to
understanding the physical mechanisms of solar eruptions, which impact the
heliosphere and planetary atmospheres. Strongest disturbances in the Earth's
space environments are often associated with large-scale flux ropes from the
Sun colliding with the Earth's magnetosphere, leading to adverse, sometimes
catastrophic, space-weather effects. However, it remains elusive as to how a
flux rope forms and evolves toward eruption, and how it is structured and
embedded in the ambient field. The present paper addresses these important
questions by reviewing current understandings of coronal flux ropes from an
observer's perspective, with emphasis on their structures and nascent evolution
toward solar eruptions, as achieved by combining observations of both remote
sensing and in-situ detection with modeling and simulation. It highlights an
initiation mechanism for coronal mass ejections (CMEs) in which plasmoids in
current sheets coalesce into a `seed' flux rope whose subsequent evolution into
a CME is consistent with the standard model, thereby bridging the gap between
microscale and macroscale dynamics.
