A comprehensive understanding of the fundamental physical characteristics and the intricate relationships among composition, microstructure, magnetic properties, and hyperfine interactions is crucial for the rational design of novel magnetic materials. Building on this framework, the study explores Zn-, Mn-, and Co-doped maghemite/magnetite nanoparticles by Mössbauer spectroscopy, emphasizing how synthesis pathways affect spin dynamics and magnetic anisotropy. Hematite nanoparticles are examined as a model system exhibiting a magnetic transition from antiferromagnetic to weakly ferromagnetic ordering, showing analogous characteristics to the progressive evolution from collective spin ordering to superparamagnetic relaxation in the nanoparticles, and even to martensitic-like transitions, despite their distinct magnetic nature. The presentation further discusses capabilities and limitations of Mössbauer spectroscopy in studies of complex magnetic materials, along with recent methodological advances in the Laboratory of Mössbauer Spectroscopy in Troja.