WE PROPOSE TO CONTINUE OUR HIGHLY SUCCESSFUL COVERAGE OF THE COOLING NEUTRON STAR IN MAXI J0556-332 WHICH WAS STRONGLY HEATED DURING A NEAR/SUPER-EDDINGTON OUTBURST IN 2011/12 AND AGAIN DURING A SMALLER OUTBURST IN 2016. OUR QUIESCENT OBSERVATIONS WHICH REVEALED AN EXTRAORDINARILY HOT AND RAPIDLY COOLING NEUTRON STAR HAVE PROVIDED UNIQUE INSIGHTS INTO NEUTRON-STAR STRUCTURE AND IN PARTICULAR INTO THE NATURE OF HEAT SOURCES IN THE SHALLOW OUTER CRUST. RECENT OBSERVATIONS SUGGEST THAT THE ONGOING COOLING TREND IS NOW DOMINATED BY HEAT INDUCED DURING THE FIRST OUTBURST IN DEEPER CRUSTAL LAYERS. WE REQUEST A 106 KS XMM-NEWTON OBSERVATION TO INVESTIGATE IF THE REMARKABLE PROPERTIES OF THE OUTER CRUST EXTEND TO DEEPER LAYERS WHERE MATTER REACHES NUCLEAR DENSITY.