  The non-Hermitian skin effect is an iconic phenomenon characterized by the
aggregation of eigenstates near the system boundaries in non-Hermitian systems.
While extensively studied in one dimension, understanding the skin effect and
extending the non-Bloch band theory to higher dimensions encounters a
formidable challenge, primarily due to infinite lattice geometries or open
boundary conditions. This work adopts a point-gap perspective and unveils that
non-Hermitian skin effect in all spatial dimensions originates from point gaps.
We introduce the concept of uniform spectra and reveal that regardless of
lattice geometry, their energy spectra are universally given by the uniform
spectra, even though their manifestations of skin modes may differ. Building on
the uniform spectra, we demonstrate how to account for the skin effect with
generic lattice cuts and establish the connections of skin modes across
different geometric shapes via momentum-basis transformations. Our findings
highlight the pivotal roles point gaps play, offering a unified understanding
of the topological origin of non-Hermitian skin effect in all dimensions.
