  We present a concise review of the recent development of relativistic
hydrodynamics and its applications to heavy-ion collisions. Theoretical
progress on the extended formulation of hydrodynamics towards
out-of-equilibrium systems is addressed, emphasizing the so-called attractor
solution. On the other hand, recent phenomenological improvements in the
hydrodynamic modeling of heavy-ion collisions with respect to the ongoing Beam
Energy Scan program, the quantitative characterization of transport
coefficients in the three-dimensionally expanding quark-gluon plasma, the fluid
description of small colliding systems, and some other interdisciplinary
connections are discussed.
