  Colloids play an important role in fundamental science as well as in nature
and technology. They have had a strong impact on the fundamental understanding
of statistical physics. For example, colloids have helped to obtain a better
understanding of collective phenomena, ranging from phase transitions and glass
formation to the swarming of active Brownian particles. Yet the success of
colloidal systems hinges crucially on the specific physical and chemical
properties of the colloidal particles, i.e. particles with the appropriate
characteristics must be available. Here we present an idea to create particles
with freely selectable properties. The properties might depend, for example, on
the presence of other particles (hence mimicking specific pair or many-body
interactions), previous configurations (hence introducing some memory or
feedback), or a directional bias (hence changing the dynamics). Without
directly interfering with the sample, each particle is fully controlled and can
receive external commands through a predefined algorithm that can take into
account any input parameters. This is realized with computer-controlled
colloids, which we term cybloids - short for cybernetic colloids. The potential
of cybloids is illustrated by programming a time-delayed external potential
acting on a single colloid and interaction potentials for many colloids. Both
an attractive harmonic potential and an annular potential are implemented. For
a single particle, this programming can cause subdiffusive behavior or lend
activity. For many colloids, the programmed interaction potential allows to
select a crystal structure at wish. Beyond these examples, we discuss further
opportunities which cybloids offer.
