A summer Institute for Cooperative Emulsion Research was jointly sponsored by the National Science Foundation and the University of Chicago during the months of July and August, 1956. The work of the Institute was made possible through the great encouragement which we have received from the National Science Foundation and the authorities of our own University. It was of particular importance in this connection that the Nuclear Physics Branch of the Office of Naval Research, Washington, D.C., gave full support to the program of the Summer Institute and that we received permission to use microscopes and other equipment owned by the US Navy.