Different forms of nanoscale communications and networking are a reality, thanks to recent advances in nanotechnology, integrated circuit design, antenna miniaturization, and synthetic biology. As first nanonetwork systems start to appear, one of the main challenges from the communications perspective is the development of effective and efficient means for medium access control, where this chapter sets the focus. Existing techniques cannot be applied directly in nanoscale scenarios because of the extreme differences with respect to traditional contexts. Here, these differences are reviewed for three 186representative nanonetwork paradigms spanning several transmission ranges, communication mechanisms, energy policies, or mobility characteristics. Then, their impact on the design of appropriate shared medium management procedures is analyzed through a brief survey of protocols proposed in the literature.