Simulation of high-resolution continuum maps towards Sgr B2(N), left, and Sgr B2(M), right with a resolution of 0.1′′ at decreasing wavelengths from top to bottom. Observations like this are possible with ALMA. The red circles in the maps in the top row indicate the location and extent of the Hii regions. Maps having black dashed (and solid) contours are affected by optical thickness. The black dashed contours in maps of Sgr B2(N) indicate where the τ = 1 surface equals −3.50, and –3.39 pc, respectively. The black (dashed and solid) contours in maps of Sgr B2(M) show where the τ = 1 surface equals −1.0, −0.05, and 0.0 pc, respectively. These maps indicate that, especially for Sgr B2(M), the free-free emission contributes significantly at 3 and 2 mm. On the other hand, the dust becomes optically thick at ~0.5 mm for Sgr B2(M), and already at ~1 mm for Sgr B2(N).