Glenn T. Seaborg and astronomer Clyde W. Tombaugh, discoverer of the planet Pluto, at a press conference at the Sandia National Laboratory in Albuquerque, New Mexico 25th Anniversary of the discovery of plutonium with (from left to right) Glenn Seaborg, Arthur C. Wahl and Edwin McMillan.
In June 1991 I happened to meet in Albuquerque the discoverer of the planet Pluto, who was still alive, Clyde Tombaugh. He had discovered the planet Pluto in 1930 when he was only 24 years old. Here we are at a press conference, the discoverers of Pluto and plutonium. And on the 25th anniversary, February of 1966 that would be, of the discovery of plutonium, the room in Gilman Hall, room 307, was declared a historic national landmark. Here is the plaque that is now on that door. If you want to go up there and see it, it's still there. By some miracle Gilman Hall still stands, although the other chemistry buildings have been torn down.
Glenn T. Seaborg in 307 Gilman Hall.
Here I am, at about 20 years after the discovery of plutonium, in that room, room 307 Gilman Hall, on one of my trips back from Washington when I was serving at chairman of the AEC. The room was pretty much the same as it was when we discovered plutonium.

Demonstration of fission of Pu-239 by Kennedy, Seaborg, Segrè, and Wahl on March 28, 1941
Then we went on, joined by Segrè, and bombarded a lot of plutonium with a lot of neutrons and produced a half a microgram, using the 60-inch cyclotron and then using the 37-inch cyclotron showed that it underwent fission with slow neutrons, with a cross section about the same as the fissionable isotope of uranium, U235, which meant, of course, that it had this potential to be the explosive ingredient for an atomic bomb. We reported that to Washington and that was the basis of the plutonium project of the Manhattan District. That measurement was made on March 28, 1941 and on the 25th anniversary of that, March 28, 1966, Segrè and I presented that sample, that half microgram sample with its rare earth carrier, to the Smithsonian where you can see it now on display in the Science in American Life exhibit.
Glenn T. Seaborg and Emilio Segrè presenting plutonium sample to Smithsonian Institution

I kept it in this cigar box those intervening years. As Darleane has said, I worked as Gilbert N. Lewis' research assistant. He was an inveterate smoker of cigars, lit one off the end of one after the other, and I inherited these cigar boxes and used one of them to keep this sample in.