  In the context of quantum fields in time dependent classical backgrounds, we
notice that the number of created particles with a given momentum largely
deviates about its mean value. Guided with this observation we use a complete
orthonormal family of localized wave packets to calculate the deviations in the
number and energy densities of particles produced in a volume of a given size
during reheating. It turns out that at the end of reheating there exists (in
general tiny) spatial variations in these densities on Hubble length scales
over which local interactions are incapable of restoring homogeneity. This
signals the destruction of perfect homogeneity attained after inflation due to
the quantum nature of particle production process in reheating.
