  Supernova Remnants and Pulsar Wind Nebulae are among the most significant
sources of non-thermal X-rays in the sky, and the closest laboratories where
relativistic plasma dynamics and particle acceleration can be investigated.
Being strong synchrotron emitters, they are ideal candidates for X-ray
polarimetry, and indeed the Crab nebula is up to present the only object where
X-ray polarization has been detected with a high level of significance. Future
polarimetric measures will likely provide us crucial informations on the level
of turbulence that is expected at the particle acceleration sites, together
with the spacial and temporal coherence of the magnetic field geometry,
enabling us to set stronger constraints on our acceleration models. In PWNe it
will also allow us to estimate the level of internal dissipation. I will
briefly review the current knowledge on the polarization signatures in SNR/PWNe
and I will illustrate what can we hope to achieve with future missions like
IXPE/XIPE.
