  Pulsar wind nebulae (PWNe) are the synchrotron bubbles inflated by the
rotational energy of a neutron star. Observing variability within them has
previously been limited to cases of significant brightening, or the few
instances where transient features are interpreted in terms of intrinsic motion
or associated with variability from the pulsar. Jet and torus morphology are
also only visible in cases of differing brightness with respect to the
surrounding nebula and favourable alignment with our line of sight. Spectral
map analysis involves binning observations with an adaptive algorithm to meet a
signal limit and colouring the results based on the desired model parameter
fits. Minute changes in spectral index become therefore apparent even in cases
where brightness images alone do not suggest any underlying changes. We present
a Chandra X-ray study of the PWNe in G21.5-0.9, Kes 75, G54.1+0.3, G11.2-0.3,
and 3C 58, using archival observations accumulated over the ~20-year lifetime
of the mission. With the spectral map analysis technique, we discover evidence
for previously unknown variability opening a new window into viewing PWNe.
