Tracking QCD instantons

In a first part, I review our detailed investigation of the prospects to discover deep-inelastic processes induced by small QCD-instantons at HERA. This includes the essence of our calculations based on instanton-perturbation theory, crucial lattice constraints and a confrontation of the recent intriguing (preliminary) search results by the H1 collaboration with our predictions. In a second part, I report on two ongoing attempts towards a better understanding of the role of larger-size instantons in the QCD-vacuum and in high-energy (diffractive) scattering processes, respectively: The striking suppression of larger-size instantons in the vacuum is attributed to a residual conformal inversion symmetry, and a precocious lack of ``color transparency in the one-instanton contribution to the color-dipole scattering picture is emphasized