  The counterflow superfluidity (CSF) was predicted two decades ago.
Counterintuitively, while both components in the CSF have fluidity, their
correlated counterflow currents cancel out leading the overall system to an
incompressible Mott insulator. However, realizing and identifying the CSF
remain challenging due to the request on extreme experimental capabilities in a
single setup. Here, we observe the CSF in a binary Bose mixture in optical
lattices. We prepare a low-entropy spin-Mott state by conveying and merging two
spin-1/2 bosonic atoms at every site and drive it adiabatically to the CSF at
$\sim$ 1 nK. Antipair correlations of the CSF are probed though a site- and
spin-resolved quantum gas microscope in both real and momentum spaces. These
techniques and observations provide accessibility to the symmetry-protected
topological quantum matters.
