Phenotypic heterogeneity is a diversity that occurs independently of genetic or environmental variation. Nowadays, the prevalence of drug resistance pathogen increasing from time to time whereas new drugs entering the market is getting low. A recent study identified an epigenetic basis for growth heterogeneity allows some cancer cells to survive chemotherapy. Growth heterogeneity also contributes to chemoresistance in tumors (Jeff Settleman et al., 2010). Therefore, understanding the phenotypic nature of the organism or cells helps to design the effective drugs by developing drugs that attack various population subsets rather than targeting the population average.