Hybrid Approaches: Integration of Gene Expression data into a GEM model
			Following the introduction of GEM Models and the high-throughput approaches for extracting 
			genome-wide expression pattern of a cell (e.g. DNA microarray, ChIP-Seq and RNA-Seq), 
			the new challenge for a better prediction of the metabolic activities of different cells appeared; 
			how gene expression data can be integrated into GEM models. The conflation of genetic expression data and GEM models 
			leads to a better and deeper understanding of the occurrence of certain changes in gene expression under 
			different conditions.
			
			First, Covert and Palsson addressed this issue by Boolean approach in 2002.