Like ordinary molecules are composed of atoms, colloidal molecules consist of
several species of colloidal particles tightly bound together. If one of these
components is self-propelled or swimming, novel "active colloidal molecules"
emerge. Active colloidal molecules exist on various levels such as
"homonuclear", "heteronuclear" and "polymeric" and possess a dynamical function
moving as propellers, spinners or rotors. Self-assembly of such active
complexes has been studied a lot recently and this perspective article
summarizes recent progress and gives an outlook to future developments in the
rapidly expanding field of active colloidal molecules
