Experimental evidence for the transformation of nanosheets of GaS and GaSe into onion structures on UV excimer pulsed laser irradiation is presented. Few-layer GaS and GaSe on Si substrates were exposed to KrF pulsed laser with wavelength of 248 nm and the effect was studied as a function of number of laser pulses. Laser-induced dewetting of the layers results in the formation of spherical nanoparticles after 50 laser pulses. HREM images of these particles reveal the formation of onions with several concentric layers. The initial thickness of the layers controls the size of the onion cages. A mechanism of transformation of few layers to closed cage onions on UV pulsed laser irradiation is presented. © Indian Academy of Sciences.