If the trust was set up by the will (i.e. it was a "testimentary trust"), then it would be part of the estate, since it was formed after death by the same instrument (the will) which distributes the rest or balance of the estate; and also because the assets that will go to make up the trust were, like the rest of the estate, owned at death. But if it was formed pre-death (it was an "intervivos trust") then it was not owned by the decedent (person who passed away) at death (rather it was owned by the trust, which is a separate legal entity) and so is *not* part of the estate.