Understanding architecture in materials down to atomic level is a key for design and fabrication of advanced materials as devices become smaller and interfacial effects dominate performance. Aberration-corrected STEM (AC-STEM) combined with energy-loss and energy-dispersive x-ray spectroscopic techniques (EELS and EDS) provide the necessary quantitative elemental information with sub-nanometer spatial resolution. Utilizing advanced TEM holders, which can provide materials with external effects during imaging process, including thermal, stress/strain, electric field and magnetic field et. al ., in addition, enables characterizing materials with both spatially and temporally resolved perspective. This paper describes an overview of our recent progress in a characterizing a magnetic alloy, alnico, using state-of the-art electron beam characterization tools located at the Sensitive Instrument Facility (SIF) in Ames Laboratory. Alnico alloys (containing Al, Ni, Co, Ti, Fe, and Cu) show great potential for replacing the best commercial Nd-based rare-earth alloys for applications above 200°C. The coercivity of alnico depends on its nanostructure, in particular, the composition and morphology of the Al-Ni-rich, Fe-Co-rich and Cu-enriched phases that developed during spinodal decomposition. The spinodal decomposed structures are developed after a lengthy heat-treatment process, including high temperature solutionization (~1250°C), magnetic-field annealing (~840°C) to induce anisotropic growth of the SD phases, and drawing (~600-700°C) to optimize the magnetic properties. Both ex situ and in situ TEM are performed to better elucidate the relationship between processing conditions, microstructure and property. Figure 1 shows results on commercial alnico 9 alloy. The Cu-enriched phase was discovered to have a defective structure (Figs. 1a) with a gradual increase of Cu-concentration into the center of the precipitate. Geometric phase analysis (GPA) from