We report on the structure of and elemental distributions within various magnetic nano-particles synthesized using organometallic precursors. The characterization was carried out using high-resolution transmission electron microscopy (HRTEM), and electron energy loss spectroscopy (EELS), with spectral imaging to investigate elemental distributions within the particles. The crystallinity and oxidation of Fe, Co and Fe-Co particles are discussed. We observe heavy oxidation of Fe particles, while Co particles show, at most, only a thin surface layer of oxide. When Fe and Co are combined to form Fe-Co particles, they are seen to be inhomogeneous, consisting of an Fe core, surrounded by a Co-rich shell.