Topological boundaries between helical domains as a nucleation source of skyrmions in the bulk cubic helimagnet <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:mrow><mml:msub><mml:mi>Cu</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi>OSeO</mml:mi><mml:mn>3</mml:mn></mml:msub></mml:mrow></mml:math>

${\mathrm{Cu}}_{2}{\mathrm{OSeO}}_{3}$ represents a unique example in the family of B20 cubic helimagnets with tilted spiral and low-temperature skyrmion phase arising for magnetic fields applied along easy crystallographic $\ensuremath{\langle}100\ensuremath{\rangle}$ axes. Although stabilization mechanism these phases can be accounted by anisotropy, nucleation process is still an open question, since stability region displays strongly hysteretic behavior different boundaries increasing decreasing fields. Here, we address this important point using micromagnetic simulations come to conclusion that underpinned reorientation domains occurring near critical diagrams: ${H}_{C1}$, field transition between helical conical/tiled phase, ${H}_{C2}$, homogenous phase. By studying wide variety cases show domain walls may have 3D structure. Moreover, they carry finite topological charge stemming from half-skyrmions (merons) also permitting along-the-field perpendicular-to-the-field orientation. Thus, envisioned as source skyrmions form thermodynamically stable metastable lattices well networks misaligned tubes. The results numerical are discussed view recent experimental data on chiral magnets, particular, bulk helimagnet ${\mathrm{Cu}}_{2}{\mathrm{OSeO}}_{3}$.