A Chromatin immunoprecipitation (ChIP) assay is a specific type of immunoprecipitation technique used to study the DNA-protein interactions in the cell. It relies on the use of an antibody to precipitate or isolate a target protein, cofactor, transcription factor, or histone and its bound chromatin from a protein mixture that was extracted from tissues or cells. The steps involved in a ChIP assay include: Crosslinking, Cell Lysis, Chromatin Preparation, Immunoprecipitation, and DNA quantitation. 

ChIP assays enable researchers to determine the target of histone modifiers by identifying the specific location in the genome that various histone modifications are associated with. The advantage of using a ChIP assay is that it allows researchers to obtain an accurate snapshot of specific DNA-protein interactions occurring in a system.