Usually the lawyer establish a revocable trust, and trasnfer all asset into the trust. A revocable trust means the owner retains full control of asset in the trust, there is no change of control therefore it is not a tax event in US.
When the owner dies, the revocable trust becomes an irrevocable trust, that's a tax event because there is transfer of control. But in US all asset receives step-up basis so all the capital gain acquired before the death are wiped out. So the asset at the time of death has no capital gain due to step-up basis. The only tax due is estate tax (遗产税），which is 0% for asset under 11 million per person.
