Abstract: An improved microwave unit and system incorporating the unit are provided for use in tissue processing and other chemical reactions. The microwave unit is comprised of an energy source, a wavguide transmitting the microwave energy to a reaction chamber, and the reaction chamber being adapted to perform the desired chemical reaction. The unit provides gentle and uniform heating, with minimal heat loss and escape of volatile chemicals. The system may be operated continuously or batchwise, by manual operation or automatically. Preferably, an automated system is operated with continuous throughput using a robotic armature to obtain the advantages of the invention.