Recent advancements in biological nanomachines have motivated the research on nanorobotic sensor networks (NSNs), where the nanorobots are green (i.e., biocompatible and biodegradable) and touchable (i.e., externally controllable and continuously trackable). In the former aspect, NSNs will dissolve in an aqueous environment after finishing designated tasks and are harmless to the environment. In the latter aspect, NSNs employ cross-scale interfaces to interconnect the in vivo environment and its external environment. Specifically, the in-messaging and out-messaging interfaces for nanorobots to interact with a macro-unit are defined. The propagation and transient characteristics of nanorobots are described based on the existing experimental results. Furthermore, planning of nanorobot paths is discussed by taking into account the effectiveness of region-of-interest detection and the period of surveillance. Finally, a case study on how NSNs may be applied to microwave breast cancer detection is presented.