Which part of the body does not decay after death?

Good day, could you please elaborate on the concept of a body part that remains unchanged post-mortem? Specifically, which anatomical structure is known to resist the natural processes of decomposition? It's quite intriguing to ponder upon the idea of something within us remaining untouched by time's relentless march, even after our physical presence fades. Could you shed some light on this enigmatic aspect of human anatomy?