The average consumer has relied upon bidirectional RF communication for phone and internet connectivity for years. These devices are either plugged in to wall outlets or rely on large batteries that must be recharged frequently. A new generation of deeply embedded, short-range wireless applications is emerging, fueled by the extreme reductions in cost and power required for sensing and computation afforded by CMOS and MEMS process advancement. The power consumption of wireless communication links, on the other hand, has not scaled down so dramatically. Short range wireless protocols, such as Bluetooth and 802.15.4, have been developed to meet the communication needs of these applications and have already seen substantial commercial success. However, the excessive energy requirements of current commercially available radios, even those aimed at short range WPAN applications, limit the scope and inhibit the growth of the deeply embedded wireless market. A substantial reduction in energy consumption of short-range RF transceivers is necessary to make future pervasive computing applications feasible. In this work, the energetic requirements of RF wireless communication are evaluated from both purely theoretical and practical standpoints, revealing a large gap in practically achievable energy efficiency and what is offered in today's commercial market. In the context of minimizing energy per transferred data bit, each level of the physical design of wireless systems will be discussed -- from choice of modulation scheme and bandwidth, down to transceiver architectures and low-level circuit designs. Finally, the implementation and measurement results from a 2.4GHz CMOS RF transceiver prototype are presented. Benefiting from energy conscious high-level system decisions and novel circuit architectures, the transceiver achieves a low energy consumption of 1 nJ per received bit and 3 nJ per transmitted bit with 92 dB of link margin.