Ni Superalloys in Jet Engines: A Journey Through Remarkable Microstructures: The history of Ni-based superalloys in jet engines is a story of continuous innovation driven by ever more demanding operating conditions. From the first wrought and cast alloys used in early turbines, the need for higher temperature capability, creep resistance, and reliability led to major advances in alloy design and processing, including precipitation strengthening, control of grain boundaries, and increasingly complex chemistries. Among these developments, powder metallurgy routes -particularly the hot isostatic pressing (HIP) of encapsulated Ni superalloy powders- have played a key role by enabling fine and homogeneous microstructures, reduced segregation, and the manufacture of highly alloyed compositions. In parallel, the quest for maximum performance pushed the evolution from equiaxed and directionally solidified alloys to single-crystal superalloys, whose remarkable microstructures eliminate grain-boundary limitations and remain one of the most fascinating achievements in materials science for aviation turbines.