This talk reflects on the enduring impact of Professor Merlin Albert Vannice's contributions to chemical engineering, particularly in catalysis and reaction engineering. Building on foundational training under his guidance, I will highlight how core principles have shaped process development across the pharmaceutical industry- from traditional small molecule API development and manufacturing to oligonucleotide process design, modeling and PAT implementation. His influence continues through the application of rigorous, mechanism-based thinking to emerging technologies and complex systems.