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In this review, I will address the large-scale structure of molecular clouds. These objects are highly inhomogeneous, with some of the most prominent condensations within them being filaments and dense cores. To understand evolution of these denser structures, which are the locations in which star formation takes place, we have to understand the large-scale distribution of density and temperature, as well as kinematics of the molecular cloud material. These key physical parameters are all interconnected, and while it remains a real challenge to disentangle variations along the line of sight, significant progress is being made. Accurate measurement of the gas density distribution along with the velocity field is essential for answering the important question of the overall virial balance of these clouds. A long-standing question has been the source of energy for the supersonic motions observed in almosts all molecular clouds. Yet another question is the effect of the dissipation of this energy on cloud structure. I will concentrate on review of observationally-determined cloud parameters, particularly as revealed by large-area studies of gas and dust. I will also discuss the structure of molecular cloud edges, and what they can tell us about energy transport in these regions. I will include some recent results on the "CO-dark" gas in these regions traced by CII emission observed by Herschel.
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