Cyanobacteria are the potential cell factories due to their inherent capability of sequestering atmospheric CO2 and converting into useful metabolites. Exploring this characteristic feature, research groups have tried to engineer these photosynthetic organisms to produce various biofuel precursors.  While these studies provide proof of concept, commercialization will require further improvements in their productivity. We argue that promoter engineering is an important step in pathway engineering for the production of biofuels in cyanobacteria.  Promoters are the non-coding regions which are responsible for controlling the expression of gene of interest. A large number of promoters in Synechococcus elongatus PCC 7942 are under circadian control. Altering the sequence of the promoters would alter its strength; hence different levels of gene expression can be obtained. My study focuses on characterizing, identifying the regulatory regions and the suitable stretch of two most significant promoters of S. elongatus. Further engineer the sequence of the promoter to improve its strength such that it will have a significant implication in pathway engineering.