Stellar streams in the Milky Way halo are remnants of tidal debris from dwarf galaxies and globular clusters, preserved for billions of years due to their low mass and long dynamical times. The Gaia mission has revolutionized the study of these streams by providing precise astrometric and spectroscopic data for billions of stars, leading to three major breakthroughs: (1) the discovery of over 100 streams, an order of magnitude increase from previous counts; (2) the detailed kinematics of streams, enabling precise orbit and origin determination; and (3) the resolution of stream structures, revealing complex dynamical histories. These discoveries have established stellar streams as sensitive gravitational tracers of the Milky Way's dark matter halo. The Gaia era has enabled a comprehensive mapping of stellar streams and the development of numerical models to study their evolution in various cosmological scenarios. By comparing stream data with theoretical predictions, dark matter subhalos below the threshold for galaxy formation (≲10⁶ M☉) can be detected, offering the most stringent test of the cold dark matter paradigm on small scales. The Gaia mission has also transformed the discovery and characterization of streams, enabling the identification of previously undetected low-density streams and providing kinematic data for detailed studies of stream structures. The number of known streams has increased dramatically, with over 120 streams reported in the literature, and new discoveries continue to emerge. The Gaia era has provided a wealth of data for understanding the Milky Way's dark matter halo and the formation history of its stellar populations.Stellar streams in the Milky Way halo are remnants of tidal debris from dwarf galaxies and globular clusters, preserved for billions of years due to their low mass and long dynamical times. The Gaia mission has revolutionized the study of these streams by providing precise astrometric and spectroscopic data for billions of stars, leading to three major breakthroughs: (1) the discovery of over 100 streams, an order of magnitude increase from previous counts; (2) the detailed kinematics of streams, enabling precise orbit and origin determination; and (3) the resolution of stream structures, revealing complex dynamical histories. These discoveries have established stellar streams as sensitive gravitational tracers of the Milky Way's dark matter halo. The Gaia era has enabled a comprehensive mapping of stellar streams and the development of numerical models to study their evolution in various cosmological scenarios. By comparing stream data with theoretical predictions, dark matter subhalos below the threshold for galaxy formation (≲10⁶ M☉) can be detected, offering the most stringent test of the cold dark matter paradigm on small scales. The Gaia mission has also transformed the discovery and characterization of streams, enabling the identification of previously undetected low-density streams and providing kinematic data for detailed studies of stream structures. The number of known streams has increased dramatically, with over 120 streams reported in the literature, and new discoveries continue to emerge. The Gaia era has provided a wealth of data for understanding the Milky Way's dark matter halo and the formation history of its stellar populations.