  A dedicated in situ heating setup in a scanning electron microscope (SEM)
followed by an ex situ atomic force microscopy (AFM) and electron backscatter
diffraction (EBSD) is used to characterize the nucleation and early growth
stages of Fe-Al intermetallics (IMs) at 596 {\deg}C. A location tracking is
used to interpret further characterization. Ex situ AFM observations reveal a
slight shrinkage and out of plane protrusion of the IM at the onset of IM
nucleation followed by directional growth. The formed interfacial IM compounds
were identified by ex situ EBSD. It is now clearly demonstrated that the
{\theta}-phase nucleates first prior to the diffusion-controlled growth of the
{\eta}-phase. The {\theta}-phase prevails the intermetallic layer.
