Hybrid Energy-Efficient Distributed clustering (HEED) introduced by Younis and Fahmy, is a multi-hop WSN clustering algorithm which brings an energy-efficient clustering routing with unambiguous thought of energy. Different from LEACH in the manner of CH election, HEED does not select nodes as CHs arbitrarily. In HEED, CHs are periodically elected based on two important parameters: residual energy and intra-cluster communication cost of the candidate nodes. Initially, in HEED, a percentage of CHs among all nodes, Cprob, is set to assume that an optimal percentage cannot be computed a priori. The probability that a node becomes a CH is: Where Eresidual is the estimated current energy of the node, and Emax is a reference maximum energy, which is typically identical for all nodes in the network. The value of CHprob, however, is not allowed to fall below a certain threshold that is selected to be inversely proportional to Emax. Afterwards, each node goes through several iterations until it finds the CH.