Perhaps there is no moment.
Nerve cells grow, connect and start functioning as a brain.
Consciousness grows with the complexity and experience of the brain. There is nothing special about the atoms in nerve cells that science is aware of. Our model of the universe implies that most of what exists is beyond the perception of any conscious human observer. It would seem that observation is primarily internal as we can simulate almost any perception by artificial means. We are directly conscious only of the nerve activity inside our body.