Mobile ad hoc networks (MANETs) are selforganizing networks that provide rapid network connectivity in infrastructureless environments. Most routing protocols designed for MANETs assume connected networks. Such a restriction directly limits the application domains of MANETs. In this paper, we study the problem of providing time-critical data delivery in sparse ad hoc networks where network partitions can last for long periods, without imposing any restrictions on the node mobility. Supporting real-time communication with unconstrainedmobility is important to many mission-critical applications such as battle-fields and search and rescue in large-scale disaster areas. In this paper, we propose microrouting networks consisting of tiny nodes similar to sensors but without transducers (called microrouters) as a substrate for time-critical data delivery in sparse MANETs. We describe the microrouting protocol for the resulting hybrid network which exploits the fact that microrouters are stationary, but are constrained by energy and memory. We demonstrate the viability of the microrouting network architecture via detailed simulation evaluation. Our results show that microrouting networks running the microrouting protocol efficiently extend the connectivity of sparse MANETs and provide high packet delivery ratios.