This HERAcell CO2 double stack 10.6 cubic feet incubator with solid copper inner casing and fittings is used to house our culture system for growing mouse embryonic stem cells on stromal feeder layers engineered to produce a ligand which signals functional changes in T-lymphocyte precursor cells. The copper lining is important to inhibit fungal growth which can occur under the humid warm conditions needed for the growth of the cells.