A letter written by the Northamptonshire scientist who discovered DNA is expected to fetch more than £1 million at auction.
The hand-written note in which Francis Crick tells his 12-year-old son Michael of his "most important discovery" was written weeks before the public announcement of his findings in 1953.
It will go on sale next month.
Dr Crick wrote: "We have built a model for the structure of des-oxy-ribose-nucleic-acid, (read it carefully) called DNA for short."
The biologist drew a diagram for his son in the letter dated March 19, 1953, telling him: "Our structure is very beautiful."
He added: "In other words we think we have found the basic copying mechanism by which life comes from life."
Dr Crick signed the letter: "Lots of love, Daddy."
The pioneering scientist, who was from Northampton but emigrated to California, went on the win the Nobel Prize for physiology and medicine in 1962.
He died in 2004 at the aged of 88.
His son Michael said: "On March 19 my father wrote to me describing the model and its implications. I was 12 at the time and away at Bedales - a British boarding school."
He said of the discovery: "That singular moment on February 28, 1953, when all the pieces suddenly fitted together has to go down as one of the great moments in the history of science.
"The excitement of the event was beautifully captured for the first time in this perfect letter summarising the nub of the discovery in seven simple pages."
He said a significant portion of the proceeds from the sale of the letter would be donated to the Salk Institute for brain research in La Jolla, California, where Dr Crick spent 27 years after leaving the Medical Research Council in Cambridge.
The auction is being held at Christie's in New York on April 10.
It is expected to sell for between one and two million US dollars.