The nanostructure of Inconel 738LC Ni-superalloy strengthened by trimodal γ' precipitates distribution was investigated after Low Cycle Fatigue (LCF) loading at temperature 700 °C. Different microscopic techniques as Scanning Electron Microscope (SEM) equipped with STEM detector, transmission Kikuchi diffraction in the SEM, transmission electron microscope (TEM) in the bright field mode and high resolution transmission electron microscopes (HRTEM) in STEM mode were used for the characterization and quantification of superalloy nanostructure. The characteristic morphology of γ' precipitates was examined by ex-situ and in-situ Small Angle Neutron Scattering (SANS) at high temperatures. All adopted microscopic techniques indicate that the morphology of γ' precipitates distributed in the γ matrix as received state corresponds to two types, i.e. large cuboid-like precipitates with the size around 670 nm, and the spherical precipitates with the diameter 52 nm. After the LCF tests at temperature 700 °C, the ex-situ SANS measurement yielded additional scattering intensities coming from another small γ' precipitates with estimated size up to 10 nm. Thin foils were observed in SEM equipped with STEM detector, in TEM and HRTEM. These observations documented the size 7 nm and evolution of distribution of these precipitates. It was concluded from in-situ SANS experiments that the smallest γ' precipitates arise regardless the application of the mechanical load. These very small precipitates have profound effect on the LCF resistance of the alloy at 700 °C since dislocations are effectively pinned by these small γ' precipitates as was directly observed by STEM detector in SEM and using TEM in STEM mode.