Multi-scale 3D architecture with highly localized fluorescence contrast in photosensitive silver-containing glasses by means of femtosecond laser writing can be obtained. We will present results obtained on electron-irradiated glass samples by EPR spectroscopy and in-situ cathodoluminescence. This allowed for understanding the initial phenomena of electron deposition and charge trapping by identifying the nature of point defects and Ag species. In addition, a careful point defects analysis of fs-laser written silica glass as a function of the laser deposited energy for [50-500 fs] pulse durations was leaded highlighted the role of certain defects in the chemical etching of fused silica glass