Described is a new type of nanoparticle using the concept of self-organization of a single continuous chain to form peptidic nanoparticles. In particular, nanoparticles of the invention consist of aggregates of a continuous chain comprising two peptidic oligomerization domains connected by a linker segment. Preferred are coiled-coil oligomerization domains with a contiguous pattern of hydrophobic residues spaced 3 and 4 residues apart. The invention provides a drug targeting and delivery system comprising a functionalized peptidic nanoparticle comprising ligands capable of binding a receptor and drugs, and a method of treating or diagnosing humans using such functionalized peptidic nanoparticles. The invention further provides an antigen display system to be used as efficient vaccines comprising a functionalized peptidic nanoparticle comprising an antigen, and a method of vaccinating humans or non-human animals using such functionalized peptidic nanoparticles. The invention also provides processes for making peptidic nanoparticles and functionalized peptidic nanoparticles, and monomeric building blocks suitable for forming such nanoparticles.