Quantum Chromodynamics (QCD) as a theory of quarks and gluons (or partons) has been very successful in describing high energy hadronic and nuclear collisions for over 35 years.  QCD relates hadrons, nuclei, and their interactions to the fundamental dynamics of partons and fields.  Al Mueller has been a key player in the field of high energy hadronic and nuclear collisions for many decades. Al made groundbreaking contributions to the development of many important concepts and techniques in QCD. Among Al's most important achievements is the seminal work he had done on infrared safety and factorization in hard processes, which permitted precise quantitative QCD-based predictions for deep inelastic and hadronic scattering experiments. The successful experimental confirmation of such predictions at HERA and Tevatron helped establish QCD as the theory of strong interactions and led to a much deeper understanding of the underlying QCD dynamics in high energy collisions. For this work Al (together with George Sterman) was awarded J.J. Sakurai prize for Theoretical Particle Physics in 2003. Al has made many more contribution to the physics of strong interactions.  Al is a founding father of the field of parton saturation, which has been developing so rapidly in recent years. The results of Al's work on saturation physics led to significant progress in our understanding of small-x data produced at HERA and at RHIC, and will play a key role in the theoretical analysis of the data to be produced at the upcoming LHC experiments.