We present small angle X-ray and cryogenic transmission electron microscopy (cryo-TEM) studies of three nitrosubstituted (n-OPIMB-NO 2 , n = 7, 9 and16) bent-core liquid crystals (LCs) that form peculiar optical patterns known as B7 textures. Small angle X-ray scattering studies show two periodicities between a~3.4-4.7 nm and b X~9 -16 nm. Cryo-TEM images of about 100 nm thick films do not show the a-periodicity, but only periodicities b T that are about 1 nm smaller than b X measured in bulk by X-ray. Additionally, an intensity modulation with a period c~100-200 nm is observed. These observations can be explained by a B1-type structure, where there are half-layer step discontinuities at the boundaries of the splay domains, and where the molecules are everywhere normal to the substrate.