The invention relates to an apparatus for forming liquid droplets, such as a micro nebulizer, useful for preparing samples for subsequent analysis via MS, AA, ICP, CE/MS, and similar analytical systems. The apparatus has a mechanically stabilized inner microtube or needle, thereby ensuring controllably uniform droplet size. The mechanical stabilization is provided by securing the inner microtube or needle, such as by narrowing the inner diameter of the outer microtube or otherwise narrowing the annular intermediate space between the inner and outer microtubes for a predetermined length. Thus, the inner microtube is secured in a centered or otherwise predetermined fixed radial position, with minimum perturbation of the fluid flow. Further, a tip, when coupled with the exit end of the outer microtube, provides a region in which the sheath fluid flow in the outer microtube stabilizes prior to both exiting the tip and colliding with the liquid analyte exiting the inner microtube.