Louis Harold Gray was born on November 10th, 1905 in London, England. Professor Gray worked primarily with understanding the biological effects of radiation. Because his work was instrumental in the birth of radiobiology, the SI unit of absorbed dose was named the gray to honor him.
Biographies:
Wikipedia
LH Gray Memorial Trust
UCLA Medical Physics
More information on his work:
Review Article: the birth of the Gray Laboratory at Mount Vernon Hospital
Gray Cancer Institute
Paul Hutchinson's Blog 