By examining molecules one at a time, single-molecule techniques capture rare and asynchronous events, revealing rich mechanistic detail that complements and deepens our understanding from bulk experiments. The Squires Group at the University of Chicago specializes in creating and using new spectroscopic “windows and handles”; experimental platforms that expand our ability to directly observe and perturb single molecules. Our unique toolset enables us to record, understand, and control complex, dynamic energy transfer patterns in both natural and engineered macromolecular systems. I will present our latest updates to our single-particle spectroscopy platform, the Anti-Brownian ELectrokinetic (ABEL) trap, and highlight two recent applications to (1) understand the Orange Caroteinoid Protein (OCP)-based photoadaptation response in cyanobacteria undergoing photosynthesis, and (2) to rationally design dozens of compound fluorescent labels from a minimal set of building blocks to enable wash-free labeling and detection of dozens of molecular species in low-concentration mixtures.