Light can be confined efficiently in the high-Q, small-volume whispering-gallery-modes observed in silica microspheres. The properties of these modes have allowed us to obtain laser action with very low thresholds in Nd-doped silica microspheres. After a brief introduction to the physics of the whispering-gallery modes, we describe our recent experiments on the lasing properties of doped microspheres at room temperature and their extension at 2 K. Further projects in the field of non-linear Optics and Cavity Quantum Electrodynamics are discussed in the conclusion.