2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/185148In 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.Presented at the Ringberg Workshop on ``New Trends in HERA Physics 2001'', 17-22 June 2001; 14 pages, 12 figuresHigh Energy Physics - Phenomenologytext