PAT in lyophilization has made great strides forward in the recent past. These advances allow the process to self regulate based upon process parameters that can now be used to determine the state of the product during many of the steps of the lyophilization process.  There are now PAT devices that can instantly nucleate ice in all of the product volume instantly, devices that allow the system to react to the residual moisture in the product to advance cycle steps, devices that allow cycle development based upon physical properties of the actual product. There are “smart” software algorithms that enable R&D freeze dryers to self develop cycle recipes that can successfully dry products.  There are devices that spectroscopically measure the doppler effect of water molecules through the main vacuum valve between chamber and condenser and allow the rate of freeze drying to be monitored and controlled, and devices can compare the pressure rise or evolution of the desorbed gaseous water during secondary drying to be used as the endpoint of the cycle.  There are NON SIP humidity measuring systems that can measure the dew point in the rarified atmosphere in the freeze dryer, and can be used for endpoint determination.