Despite significant interest in persistent luminescence materials, the focus of all recent works remains on the exploitation of materials in powder form. Here, a new point of view based on persistent luminescence in single crystals is presented. The garnet crystals [(Gd 0.67 Y 0.33) 3-x Ce x)](Al 2-y Cr y)Ga 3 O 12 and [(Gd 0.33 Y 0.67) 3-x Ce x ](Al 2-y Cr y)Ga 3 O 12 (GYAGG) codoped with Ce 3+ and different concentrations of Cr 3+ have been elaborated and their persistent luminescence properties are fully characterized within this work. The persistent luminescence of Ce 3+ , Cr 3+-codoped GYAGG single crystals is optimized due to their high optical quality, very good crystallinity and a volume effect where the whole material can be excited and charged by the excitation light. Furthermore, thanks to their transparency, robustness and homogeneity; in-depth optical spectroscopy characterization is possible, shedding light on the mechanism responsible for the afterglow.