This lecture covers the development of MIXSEL2, a high-performance optically pumped semiconductor laser, discussing its design, performance, and applications in precision engineering for health, security, energy, and the environment. The lecture delves into the engineering of multi-scale systems, emphasizing the transition of innovative technologies from research labs to practical daily use. Key topics include frequency comb stabilization, semiconductor thin disk lasers, silicon nitride properties, and the advancements in gigahertz frequency comb sources.