This article examines the current research in nano communication networks specifically Molecular Communication (MC).Molecular Communication is an emerging communication paradigm where molecules are used to exchange information. Unlike traditional communication paradigms, molecules are transmitted as messages between biological nano machines. Communication between biological living cells is as old as history of man-kind. Similarly molecular communication inside human body also has long history. MC provides a number of bio medical and other applications where communication can be understood by taking inspiration from communication between biological cells i.e., bio-inspired. Key research challenges in molecular communication include design of system components and mathematical modeling of each system component as well as entire systems. Recent research in molecular communication and its propagation medium has been reviewed in this article.