A tray containing cancer cells sits on an optical microscope in the Nanomedicine Lab at UCL's School of Pharmacy in London

 
A tray containing cancer cells sits on an optical microscope in the Nanomedicine Lab at UCL
A tray containing cancer cells sits on an optical microscope in the Nanomedicine Lab at UCL's School of Pharmacy in London May 2, 2013. REUTERS/Suzanne Plunkett