Abstract: A spectral minimal partition of a manifold is a decomposition into disjoint open sets that minimizes a spectral energy functional. It is known that bipartite spectral minimal partitions coincide with nodal partitions of Courant-sharp Laplacian eigenfunctions. However, almost all minimal partitions are non-bipartite. To study those, we define a modified Laplacian operator and prove that the nodal partitions of its Courant-sharp eigenfunctions are minimal within a certain topological class of partitions. This yields new results in the non-bipartite case and recovers the above known result in the bipartite case. This approach is based on tools from algebraic topology, which I will illustrate by a number of examples where the topological types of partitions are characterized by relative homology calculations. This talk is based on joint work with Gregory Berkolaiko, Yaiza Canzani and Jeremy Marzuola.