The Leibovitz L-15 media were formulated to promote the cell growth in medium not balanced in CO₂. The formulations were developed with the sodium bicarbonate buffer. The Leibovitz L-15 media are buffered by a complement of salts, free base amino acids and galactose so they can be used under conditions of free gaseous exchange with the atmosphere. When properly supplemented, L-15 Medium supports established cell lines, such as HEp-2 and LLC-MK2, as well as primary explants of embryonic and adult human tissue. Many viruses also have been successfully cultivated in this medium.