Hi that is an easy question because others also asked the question. When Jesus Christ talked about the Regeneration or the new world at Matthew 19:27-29 (TLB), basically meaning the new heavens and the new earth, Isaiah 65:17-19. We acknowledge the human body we already have everything, arms legs etc... But at the Second Coming of Christ a Re-creation or Regeneration will be create certain changes, that was long since been prophesied about in the Bible, Romans 6:23. This enables the body to achieve eternal life, 1 Peter 1:5. The body is waiting for the instructions to proceed a chemical map that equips the body to change into a specific kind of flesh and blood, John 4:14. This is called salvation and must be given to people by God.
The people that receive this gift from God are called the Chosen Ones or Sons of God, these are the only people that receive salvation no one else does, 1 Peter 2:9-10. They go through steps that alter their DNA and genetic information which explains how to construct the correct elements in the body to achieve eternal life, Job 33:24-26. This takes many years to complete and once it is completed people have to get used to having "a new body". Hence the term Millennium is used to refer to the time it takes to resolve the issue of salvation, Revelation chapter 21.
