The Prophet said, "All of the Sons of Adam (men) will decay except for the bone of coccyx (tailbone). From it he (man) was created and by it he will be reconstructed". Found in the Two Sahihs ...(Bukhari & Muslim) it is narrated by way of Al-A`mash from Abu Salih, from Abu Hurayrah.
Modern day science discovered in 1931:
1) The tailbone (coccyx) is the last bone at the end of your spine.
2) It is the only part of the body that does not decompose and cannot be destroyed. It cannot be finished even by burning under high temperature.
3) The first things to form inside the fertilised egg are the "primitive streak" and "node" [around 15 days later] from which all of the body of the baby originates and cells begin to form. Both of these later turn into the “tailbone”.
4) The tailbone contains mother cells for the body.
5) The first western scientist to discover the secret of the tailbone was a German named Hans Spemann (b. 1869 d. 1941) based at the University of Freiburg im Breisgau, Germany. He called the Primitive streak and node the "primary organizer" which clearly suggests that the tailbone was the basic place of origin of the human.
6) After many experiments, he concluded that there was nothing that influenced the primary organizer and it could not be destroyed.
7) Hans Spemann was awarded the “Noble Prize” in 1935 for this discovery.
8) Today, WARNEK (an organization responsible for ethical research on human fertilization & genetics) prohibits scientists to conduct experiments on fertilized eggs in which the primitive streak has already been formed. This shows the importance of the streak.
Now think, when Prophet Muhammad's information about the tailbone has been discovered by modern science, that it is where the human body is created from and that it will not be destroyed until every person shall be resurrected and reformed from it, his news that we shall be raised in another world from this tailbone shall also become true so do not neglect this fact.
Peace be upon our Master Muhammad, the Final and Truthful Messenger of Allah Almighty who informed of us this news of the unseen many hundred years ago!
In Arabic this bone is called "ajbuz-zanab" عجب الذنب