Studying the dynamic properties of the genome and other nuclear structures through time lapse microscopy of living cells can be used to obtain information on the nature of structures or the execution of important nuclear functions such as transcription, replication, and repair of DNA or processing messenger RNA.  Most nuclear structures are not visible by traditional light microscopy.  In order to study structures or proteins within the living cell nucleus, it is necessary to attach a fluorescent molecule that will cause the molecule to fluorescence that can be imaged using fluorescence microscopy.  In most cases, this involves the construction of a synthetic version of a nuclear protein that codes for a fusion of this protein with a protein that emits fluorescence.  The most commonly used fluorescent protein tag is Green Fluorescent Protein (GFP).  Two basic types of studies can be performed.  Object tracking experiments can be performed on structures large enough to be detectable as single objects.  For example, an individual gene can be studied over time.    Molecular kinetic techniques, such as fluorescence recovery after photobleaching (FRAP) and fluorescence correlation spectroscopy (FCS) measure the diffusion of molecules within the living nucleus.  These studies can reveal the relationship between visible structures and the individual molecules that they contain