Assessing the distribution of a medication in the brain is critical for the treatment of a vast range of neurological disorders, especially conditions such as Parkinson’s and Alzheimer’s diseases. To that end, scientists in the United States and Sweden are developing a method to image therapeutic antisense oligonucleotides in the brain by relying on “click chemistry,” a Nobel Prize-winning technique in which molecules are linked—clicked together—like molecular Lego blocks.