Recent studies have elucidated molecular mechanisms underlying the transcriptional control of metabolism in complex metabolic disorders such as metabolic syndrome and atherosclerosis. Chromatin immunoprecipitation (ChIP) is an important technique to study protein-DNA interactions in vivo. Chemical cross-linking of DNA and its associated proteins, followed by chromatin shearing, immunoprecipitation of a protein of interest, DNA isolation, and PCR interrogation, can identify specific interactions between protein and DNA or sites of histone epigenetic alteration. Transcription factors and epigenetic modifications are key determinants of transcription. Accordingly, ChIP experiments can provide powerful mechanistic insights to understand gene expression.