In-situ heating in an electron microscope, together with EDX and EELS analysis, was used to characterize as-deposited amorphous and transformed garnet films. It was found that upon initial crystallization, a non-uniform precipitation of a second phase occurred, altering the local chemistry and microstructure of the transformed film. In addition, to study the transformation kinetics in more detail some experiments were conducted at slower heating rates and lower temperatures. It is hoped that the data obtained can be correlated to magnetic property measurements and contribute to the development of improved processing conditions.