  The Imaging X-ray Polarimetry Explorer (IXPE), launched on December 9, 2021,
enables X-ray polarimetric observations with unprecedented sensitivity in the
2-8 keV energy range. X-ray polarization allows us to test accretion disk,
corona, and emission models of stellar-mass black holes in X-ray binaries found
predominantly in soft and hard states of accretion. Every state is dominated by
a combination of thermal disk, coronal, or reflected
emission$\unicode{x2014}$each type containing different information about the
environment around the black hole that can be understood through polarization.
In 2022, IXPE measured the polarization signatures of four stellar-mass black
holes: Cygnus X-1, 4U 1630-47, Cygnus X-3, and LMC X-1. We report on the
physical consequences of these first IXPE observations and the science driven
by this new chapter in X-ray polarimetry.
