  The new two-dimensional (2D) kagome superconductor CsV$_3$Sb$_5$ has
attracted much recent attention due to the coexistence of superconductivity,
charge order, topology and kagome physics. A key issue in this field is to
unveil the unique reconstructed electronic structure, which successfully
accommodates different orders and interactions to form a fertile ground for
emergent phenomena. Here, we report angle-resolved photoemission spectroscopy
(ARPES) evidence for two distinct band reconstructions in CsV$_3$Sb$_5$. The
first one is characterized by the appearance of new electron energy band at low
temperature. The new band is theoretically reproduced when the three
dimensionality of the charge order is considered for a band-folding along the
out-of-plane direction. The second reconstruction is identified as a surface
induced orbital-selective shift of the electron energy band. Our results
provide the first evidence for the three dimensionality of the charge order in
single-particle spectral function, highlighting the importance of long-range
out-of-plane electronic correlations in this layered kagome superconductor.
They also point to the feasibility of orbital-selective control of the band
structure via surface modification, which would open a new avenue for
manipulating exotic phenomena in this system, including superconductivity.
