Stain sample with EdU Click-it reaction solution following the instructions from the manufacturer. EdU staining is extremely bright- 30min will be sufficient to stain efficiently a 25um section. 45min staining is advised for thicker sections. The copper concentrations typically used in traditional click chemistry reactions can affect fluorophores such as GFP, mCherry, R-PE, and R-PE tandem dyes. Highly recommend to 1) stain for EdU before other antibodies (either conjugated-primaries or secondaries), and 2) stain with anti-fluorophore antibodies (such as anti-GFP).