The Dark Energy Spectroscopic Instrument (DESI) is carrying out the most ambitious spectroscopic survey ever undertaken, mapping the three-dimensional structure of the universe to shed light on dark energy and the dark sector. Key questions include determining the sum of neutrino masses, constraining the number of effective neutrino species, and testing whether dark energy is truly a cosmological constant or evolves with time. After a short overview of the cosmological context and on the DESI experiment, I will discuss recent progress on these topics, focusing in particular on results from DESI’s second data release (DR2). With DR2, DESI has now produced the largest and most detailed 3D map of the cosmos, reaching sub-percent precision on the expansion history and setting a new benchmark beyond all previous surveys. Intriguingly, the latest measurements provide hints that dark energy may not be static, with implications for standard methods of cosmological neutrino mass constraints. I will also present new approaches to cosmic web analysis that improve sensitivity to neutrino physics and offer alternatives to the conventional framework. The talk will conclude with a look at the broader impact for particle and high-energy physics, and the emerging opportunities to advance our understanding of neutrinos and the fundamental interactions that shape the universe.