Scientists get a glimpse of chemical tagging in live brains
![PET scan](https://i0.wp.com/www.sciencenews.org/wp-content/uploads/2016/08/081016_TI_epigenetics_feat_.jpg?fit=860%2C460&ssl=1)
LEAVING A MARK A new radioactive tracer molecule shows where chemical tags, called epigenetic marks, are made in the brains of healthy people. Shown is the epigenetic activity in a volunteer’s brain imaged 60 to 90 minutes after injection of the tracer.
H.-Y. Wey et al./Science Translational Medicine 2016