  We introduce a model of chemically active particles of a multi-component
fluid that can change their interactions with other particles depending on
their state. Since such switching of interactions can only be maintained by the
input of chemical energy, the system is inherently non-equilibrium. Focusing on
a scenario where the equilibrium interactions would lead to condensation into a
liquid droplet, and despite the relative simplicity of the interaction rules,
these systems display a wealth of interesting and novel behaviors such as
oscillations of droplet size and molecular sorting, and raise the possibility
of spatio-temporal control of chemical reactions on the nanoscale
