Complex sentence: In general, immunofluorescence is limited to fixed (i.e., dead) samples, analysis of structures within live cells by immunofluorescence is not possible, as antibodies cannot cross the cell membrane.
Split into simpler sentences: In general, immunofluorescence is limited to fixed (i.e., dead) samples. Analysis of structures within live cells by immunofluorescence is not possible, as antibodies cannot cross the cell membrane.