Wireless Sensor Networks (WSNs) consist of individual nodes that are able to interact with the environment by sensing or controlling physical parameters. These nodes have to collaborate to fulfill their tasks. The nodes are interlinked together and by using wireless links each node is able to communicate and collaborate with each other. There is no doubt that collision is not desirable approach in WSN. In this paper, the authors will discuss different type of challenges that faces during packet transmitted from source to destination. Here, also discuss different types of attacks in WSN.