AT123 is BGjb Medium Fitton-Jackson Modification with L-glutamine. This media supports growth as well as calcification of cartilaginous embryonic bone. AT123 was originally formulated by Biggers, Gwatkin and Judah for the growth of embryonic bone. Further the media was modified by Sylvia Fitton Jackson by enriching with the addition of amino acids and vitamins. Also, the buffering capacity of the media was increased with the addition of phosphates. This modification supports growth as well as calcification of cartilaginous embryonic bone.