Abstract: Ten years after the Laser Interferometer Gravitational-Wave Observatory (LIGO) first detected gravitational waves from two coalescing black holes, opening a new window on the Universe, design work is starting on a new generation of detectors capable of enabling a much broader range of observational science—from precision cosmology to the nature of black holes. Two successive upgrades of the LIGO detectors, A+ in 2026 followed by A# in 2029, are envisioned to fully utilize the scientific potential of the existing 4-km facilities while demonstrating the new technology essential for a next-generation 40-km gravitational-wave observatory in the United States, known as Cosmic Explorer. With larger 320-kg test masses and a tenfold longer arm length, Cosmic Explorer will push the gravitational-wave detection horizon to near the edge of the observable Universe. At design sensitivity, Cosmic Explorer will detect hundreds of thousands to millions of binary black hole and neutron star mergers per year at redshifts of up to 100, corresponding to a time when the Universe was only 0.1% of its present age. In this talk, I will survey key experimental challenges and emerging detector technologies integral to realizing LIGO A# and Cosmic Explorer, highlighting their expected evolution from small-scale laboratory experiments to deployment in tomorrow's gravitational-wave observatories.