It is nearly impossible to duplicate the various ecosystems into which GEMs may be placed, mainly because of the various environmental factors, their fluxes and changes. It is quite impossible, also to specify any microbe in precise terms of its growth, structure, function, survivability, or fate without specifying the environmental conditions (and its history) prevailing at the time when the system was tested. If field testing cannot be performed, then systems that duplicates nature as much as possible should be employed. This also includes the physiological state of the donor and recipients of recombinant DNA. Whatever system is employed, stabilization of the system should occur before the system receives any test sample. The main logical and practical way to test introduced GEMs into any ecosystem is to field test the parent strain of the GEMs that has been genetically altered with an innocuous gene(s) so that it provides a means by which it can be recovered from the ecosystem.