The gyroid is a famous triply periodic minimal surface discovered by Alan Schoen at the end of the 60s. The gyroid separates space into two identical labyrinths of passages.
Although it's hard to tell at a glance, this version is not the usual pseudo-gyroid trigonometric isosurface. It is a true tension minimized gyroid, built using "Surface Evolver" (by Ken Brakke). It has been optimized to be printed in metal at reasonable cost.