  We fully characterize the reduced dynamics of an open quantum system
initially correlated with its environment. Using a photonic qubit coupled to a
simulated environment we tomographically reconstruct a superchannel---a
generalised channel that treats preparation procedures as inputs---from
measurement of the system alone, despite its coupling to the environment. We
introduce novel quantitative measures for determining the strength of initial
correlations, and to allow an experiment to be optimised in regards to its
environment.
