We present a set of related ideas pertaining to the formulation of quantum field theory using differential graded algebras. The general framework includes first-, second- and third-quantized layers, with one layer inducing the non-commutative geometries making up the subsequent layer. We expose the ideas by following a red thread from Dirac's conformal particles, alias tensionless string partons, via Vasiiev's higher spin gravity, to topological Alexandrov--Kontsevich--Schwarz--Zarobinski sigma-models, whose degrees of freedom are operator algebras that arise on defects on the source manifold embedded into branches of target space, including perturbatively defined massless particle states and holographic duals.