Two Americans and a German shared the Nobel Prize in physiology or medicine this year.
Americans James E. Rothman and Randy W. Schekman, and German Thomas C. Sudhof were awarded the prize Monday for discoveries of how the body's cells decide when and where to deliver the molecules they produce.
The Nobel Assembly said the three "have solved the mystery of how the cell organizes its transport system."
Their work focuses on tiny bubbles inside cells called vesicles, which move hormones and other molecules within cells and sometimes outside them, such as when insulin is released into the bloodstream.
Disruptions of this delivery system contribute to diabetes, neurological diseases and immunological disorders.
Rothman, a professor at Yale University, detailed how protein machinery allows vesicles in cells to fuse with their targets to permit the transfer of molecular cargo.
Schekman, a professor at the University of California, Berkeley, was honored for discovering a set of genes required for the "vesicle traffic."
Sudhof, a professor at Stanford University, showed how vesicles are instructed precisely when to release molecules.
Schekman and Sudhof also are investigators at Howard Hughes Medical Institute.
Monday's ceremony at the Karolinska Institute in Stockholm, Sweden, will be followed by the announcement of the physics prize Tuesday, the chemistry prize Wednesday and the economics prize on October 14.
The Nobel Peace Prize will be awarded in Oslo, Norway, on Friday. The prize for literature will be awarded on a date to be announced later. Each prize comes with 8 million Swedish kronor ($1.2 million).
Swedish industrialist Alfred Nobel created the prizes in 1895 to honor work in physics, chemistry, literature and peace. The first economics prize was awarded in 1969.
In 2012, the medical Nobel Prize was awarded to Sir John B. Gurdon of England and Shinya Yamanaka of Japan for work on reprogramming cells. Their work paved the way for treatment breakthroughs.