This document summarizes and reviews several hierarchical-based routing protocols for wireless sensor networks. It begins with an introduction to wireless sensor networks and discusses how routing is an important mechanism for maximizing network lifespan by reducing energy consumption during communication. It then categorizes different routing techniques in wireless sensor networks, focusing on hierarchical-based routing protocols. Several popular hierarchical routing protocols are described in detail, including LEACH, PEGASIS, and HEED. For each protocol, the document outlines the basic routing mechanism, advantages, and limitations. The overall purpose is to provide an overview and comparison of hierarchical routing techniques for improving energy efficiency in wireless sensor networks.