  In this article we present high-resolution angle-resolved photoemission
(ARPES) spectra of the heavy-fermion superconductor URu$_2$Si$_2$. Measurements
as a function of both excitation energy and temperature allow us to disentangle
a variety of spectral features, revealing the evolution of the low energy
electronic structure across the hidden order transition. Already above the
hidden order transition our measurements reveal the existence of weakly
dispersive states below the Fermi level that exhibit a large scattering rate.
Upon entering the hidden order phase, these states transform into a coherent
heavy fermion liquid that hybridizes with the conduction bands.
