  Using parametric conversion induced by a Shapiro-type resonance, we produce
and characterize a two-mode squeezed vacuum state in a sodium spin 1
Bose-Einstein condensate. Spin-changing collisions generate correlated pairs of
atoms in the $m=\pm 1$ Zeeman states out of a condensate with initially all
atoms in $m=0$. A novel fluorescence imaging technique with sensitivity $\Delta
N \sim 1.6$ atom enables us to demonstrate the role of quantum fluctuations in
the initial dynamics and to characterize the full distribution of the final
state. Assuming that all atoms share the same spatial wave function, we infer a
squeezing parameter of 15.3\,dB.
