Stars form within molecular clouds but our understanding of this fundamental process remains hampered by the complexity of the physics that drives their evolution. We review our observational and theoretical knowledge of molecular clouds trying to confront the two approaches wherever possible. After a broad presentation of the cold interstellar medium and molecular clouds, we emphasize the dynamical processes with special focus to turbulence and its impact on cloud evolution. We then review our knowledge of the velocity, density and magnetic fields. We end by openings towards new chemistry models and the links between molecular cloud structure and star-formation rates.

中文翻译：

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湍流的分子云

恒星在分子云中形成，但我们对这一基本过程的理解仍然受到驱动其演化的物理学复杂性的阻碍。我们回顾了我们对分子云的观察和理论知识，试图尽可能应对这两种方法。在广泛介绍了冷星际介质和分子云之后，我们强调了动力学过程，特别关注湍流及其对云演化的影响。然后我们回顾我们对速度、密度和磁场的了解。我们以对新化学模型的开放以及分子云结构与恒星形成率之间的联系作为结尾。