The Invar alloys are situated in the boundary zone between the alloys showing the martensitic transformation and the alloys without it in the Fe-Ni system. The experiments, inclusive of the Mössbauer effect measurement, showed that this phase relation results in bringing an essential inhomogeneity into this type alloy, which causes the corresponding variety of magnetic states in it ; this is closely related to the anomalous properties of these alloys. That is, some transitional structures between the martensitic transformations γ ⇄ α play a fundamental role in the Invar-problem