Looking deeper into vertebrate development

Magnetic resonance imaging (MRI)is a non-invasive imaging method that provi des three-dimensional (3-D) images of the internal structure of opaque obje cts, such as humans and mice. In optimal situations, spatial resolution can approach the micron level. Arbitrarily oriented single-slice images can be obtained in seconds, with full 3-D volume images taking tens of minutes to collect. The exquisite sensitivity of MRI to the local physical and chemic al environment provides a wide range of mechanisms giving rise to intrinsic contrast in the MR experiment thus providing images with dramatic differen ces between different tissue types (e.g white vs grey matter myelinated vs unmyelinated fibres, and brain parenchyma vs ventricles). The recent advent of physiologically sensitive MRI contrast agents opens trp a wealth of new avenues of study, even including the in vivo imaging of gene expression.