By manipulating the nucleation and growth of solid materials, the synthesis of various sophisticated nanostructures has been achieved. Similar methodology, if applied to liquid, could enable the mass-production and control of ultra-small droplets at the scale of nanoparticles (10 -18 L or below). It would be highly desirable since droplets plays a fundamental role in numerous applications. Here we present a general strategy to synthesize and manipulate nanoscale droplets, similar to what has been done to solid nanoparticles in the classis solution-synthesis. It was achieved by a solute-induced phase separation which initiates the nucleation of droplets from a homogeneous solution. These liquid nanoparticles have great potentials to be manipulated like their solid counterparts, borrowing from the vast methodologies of nanoparticle synthesis, such as burst nucleation, seeded growth and co-precipitations. LNPs also serve as a general synthetic platform, to fabricate nanoreactors, drug-loaded carriers, and other hollow nanostructures with a variety of shell materials.