Maintenance of the delicate balance of the osmotic forces between the intracellular and the extracellular milieu is as essential to life as is the maintenance of the transmembrane potential to the process of life. The development of a microprobe capable of continuous monitoring of tissue osmolality will provide the physician treating a patient with head injury the necessary online information of the progression of the disease, the severity of the disease, and the effectiveness of therapeutic procedures in ameliorating the process. This will be invaluable in guiding the therapeutic interventions that are necessary. Luna Innovations and a team of researchers propose to develop a microprobe device, no more than 1 mm in diameter, that will enable the continuous measurement of brain tissue osmolality. The Phase I program will focus on the development and in vitro testing of the microprobe. During the Phase II program, the Luna team will begin testing of the probe in animal models.