For more than a century, physics has known 0f a puzzling coniiict between the T- asymmetry 0f thermodynamic phenomena and the T-symmetry 0f the underlying microphysics 0n which these phenomena depend. This paper provides a guide t0 the current status of this puzzle, distinguishing the central issue from various issues with which it may be confused. It is shown that there are two competing conceptions of what is needed t0 resolve the puzzle of the thermodynamic asymmetry, which differ with respect t0 the number of distinct T-asymmetries they take t0 be manifest in the physical world. On the preferable one-asymmetry conception, the remaining puzzle concerns the ordered distribution of matter in the early universe. The puzzle 0f the thermodynamic arrow thus becomes a puzzle for cosmology.