Additional Study Information: This is a Phase 3 multi-center open label randomized clinical trial. The purpose of this study is to learn more about which anti-rejection (or immunosuppressive) medications best protect infants, children, adolescents, and young adults after they have had a heart transplant. Two different drug regimens will be will be compared. All of these drugs are FDA-approved for adults, but not for children. Subjects will be randomized into two groups:(1) One group will receive everolimus in combination with lower doses of tacrolimus(2) One group will receive full dose tacrolimus in combination with (Mycophenolate Mofetil) MMFParticipation will last for 36 months. The study has been designed so that study visits will be coordinated with routine clinical care.