Overview of B-field structures (red segments) in the W51 e2/e8 region with resolutions from about θ ∼3″ to 0.″1, covering scales from about 0.5 pc to 540 au. Contours are dust continuum. Panels from left to right display the distinct regimes as discussed in Section 5.1: envelope-to-core scale, global-collapsing-core scale, local-collapsing-core scale, and accreting-dust-lane scale. In panel (a) contours are 3, 6, 10, 20, 30, 40, … × σ, where 1σ is 27 mJy beam⁻¹ with θ ∼ 2.″7 × 2.″0 at a wavelength λ around 1.3 mm. Contours are 3, 6, 10, 20, 35, 50, 65, 80, 95, … × σ, where 1σ is 75 mJy beam⁻¹ with θ ∼ 2.″13 × 1.″88 and λ ∼ 0.87 mm in panel (b), 60 mJy beam⁻¹ with θ ∼ 0.″7 × 0.″6 and λ ∼ 0.87 mm in panels (c) and (d), 6 mJy beam⁻¹ with θ ∼ 0.″28 × 0.″26 and λ ∼ 1.3 mm in panels (e) and (f), and 1.2 mJy beam⁻¹ with θ ∼ 0.″11 × 0.″10 and λ ∼ 1.3 mm in panels (g) and (h). Panels (b) to (f) are adapted from Koch et al. (2018).