A method of producing a lasing microsource of colloidal nanocrystals. The method includes the steps of preparing a nanocrystal solution in a solvent; depositing at least a drop of the nanocrystals solution with a drop volume below 1 nl on a flat substrate; and evaporating the solvent to dryness thereby to obtain at the edge of the evaporated drop a single annular stripe including a domain wherein the nanocrystals are arranged in an ordered array, wherein the ordered nanocrystals in the domain constitute an active region capable of lasing and the radially inner and outer edges of the stripe define a resonant cavity in which the active region is inserted.