Sterile Products may be broadly classified into two main categories, according to the manner in which they are produced: those which are sterilized after the product has been filled and sealed in the final container(s) ("terminally sterilized" products) and those where the sterilization stage (or stages) takes place is it before or after the bulk product filled in to final container. In this latter instance, all subsequent processing (typically, the filling and sealing operations) must be conducted aseptically in order to prevent recontamination of the sterilized product. The two most common pharmaceutical applications of aseptic processing methods are (a) the filling of liquid products following sterilization by filtration and (b) the filling of previously sterilized bulk powder products. An aseptic processing operation should be tested using a microbiological growth medium (media fill) during lyophilized injection formulation, filling, loading, lyophilisation, stoppering, and unloading activities.