Genetic engineering cell models are versatile tools to study gene functions, drug discovery, drug testing, disease modeling, and numerous other applications. These models are widely used in current biology, functional genome screening, cell-based human hereditary disease modeling, epigenomic studies, and visualization of cellular processes. CRISPR, the newly developed system has emerged as the most popular methodology to establish precise genetic modifications. Compared to other systems of genetic engineering, CRISPR offers researchers more control over the expression of the transgene both in terms of the time of expression, the amount of expression, and precise control over the modification.