Nature Med. doi:10.1038/nm.1971 (2009)

A technique for imaging tissues in three dimensions can be used to visualize the tumour microenvironment in greater detail than previous methods. Brett Bouma, Rakesh Jain and their colleagues at Harvard Medical School and Massachusetts General Hospital in Boston imaged various tumour types using a system called optical frequency domain imaging. It involves scanning a laser beam with shifting wavelengths over a tissue sample, measuring the properties of the reflected light across depths, and processing the signals to reveal three-dimensional perspectives. The image shows the system of blood vessels in a mouse brain with a tumour at a depth of 2 millimetres.