Synchronization in large populations of interacting elements has been observed in different disciplines such as system biology, neuroscience, computer science, and engineering. During the past decades, many efforts have been devoted to understand the synchronization phenomena from the complex networks point of view. Generally, the problem of optimizing synchronization is challenging due to the fact that macroscopic dynamics depend both on the topology of the interaction network and dynamics of the

	individual systems. In this talk  we study the effects of directionality on network synchronization by assigning directions to the links of an undirected network. We show that, the way we assign directions to the links to enhance the synchronization depends on both the undirected topology of the graph and intrinsic frequencies of the nodes.