Wireless mesh network (WMN) is a key technology for supporting a variety of application scenarios. Recently, it evolves toward a multi-radio multi-channel (MR-MC) WMN architecture, which can improve network performance by equipping each node with multiple radio interfaces and by using multiple non-overlapping channels. This evolution poses new challenges on network design. Specifically, topology control (TC), one of the fundamental research topics in WMNs, has also received extensive attention in MR-MC WMNs. This article presents an overview of TC mechanisms in the existing literature with emphasis on the mutual dependence of TC on other networking issues such as power control, channel assignment, routing, and directional antennas.