Simplify the following text for a Grade 5 native English-speaking person.
Original: In 2002 , the Nobel Prize in Physiology or Medicine was awarded to Sydney Brenner , H. Robert Horvitz and John Sulston for their work on the genetics of organ development and programmed cell death in C. elegans .
Simplified: In 2002 , the Nobel Prize for Medicine was awarded to Sydney Brenner , H. Robert Horvitz , and John E. Sulston for their work on how C. elegans 's genes cause it to grow and cause some of its cells to die .