In preparation for FLIM-FRET analysis, the appropriate donor and acceptor components must be introduced into live or fixed cells. The method of introduction depends on the nature of the components and the state of the cells. For example, plasmid DNAs encoding a protein of interest fused to a variant of GFP may be introduced into live cells by transfection or microinjection, whereas labeled antibodies are delivered by microinjection. - [Read Probing Protein Interactions Using GFP and FRET Protocol]