A concept for embedding substructures—such as fibers and membranes—into hyperelastic bulk materials is proposed, building on and generalizing [1–3]. The bulk domain is endowed with level-set functions whose isosurfaces and isolines represent the geometries of the embedded substructures. Each level-set function implicitly defines an infinite family of continuously embedded, homogenized substructures. This framework enables advanced modelling of anisotropic materials, including timber, biological tissues, layered rocks, composites, and textiles. Mechanical models are first formulated at the level of individual fibers and membranes, extended to the corresponding substructure families, and coupled to the bulk domain [1, 2]. The bulk domain itself is decribed based on classical homogeneous, isotropic, hyperelastic material models. However, due to the coupling with the substructure models, a new class of anisotropic material models is obtained. For numerical analysis, the bulk domain is discretized with standard, possibly higher-order, finite elements that need not align with the embedded level sets, as in fictitious-domain methods (FDMs). However, while sharing the unfitted-mesh philosophy of FDMs, the present approach avoids their typical challenges and, following [1], is termed Bulk Trace FEM. Boundary conditions and numerical integration are handled as in classical FEM, with no stabilization required. Numerical results in various settings confirm the effectiveness of the proposed substructure models, achieving optimal higher-order accuracy for smooth solutions. REFERENCES [1] T.P. Fries, M.W. Kaiser: On the Simultaneous Solution of Structural Membranes on all Level Sets within a Bulk Domain, Comp. Methods in Appl. Mech. Engrg., 415, 116223, 2023. DOI: 10.1016/j.cma.2023.116223 [2] M.W. Kaiser, T.P. Fries: Simultaneous analysis of continuously embedded Reissner-Mindlin shells in 3D bulk domains, Internat. J. Numer. Methods Engrg., 125, e7495, 2024. DOI: 10.1002/nme.7495 [3] T.P. Fries, J. Neumeyer, M.W. Kaiser: A new concept for embedding sub-structures via level-sets, Proceedings of the 16th World Congress on Computational Mechanics (WCCM 2024), Vancouver, Canada, 2024. DOI: 10.23967/wccm.2024.025