Prof. Martini is an observational astronomer and instrumentalist, with a focus on the evolution of galaxies and active galactic nuclei (AGN), and observational cosmology. He has done leading work in constraining the lifetimes of bright quasars, the fueling of AGN, and the demographics of AGN in clusters of galaxies, groups, and the field environment. His recent work has focused on nearby galaxy evolution and the measurement of black hole masses in luminous quasars. Prof. Martini and the Ohio State Imaging Sciences Laboratory designed and built the OSMOS and C/KOSMOS instruments, a suite of three similar medium resolution multi-object optical spectrographs for the MDM, CTIO, and Kitt Peak observatories, respectively. He is presently the Instrument Scientist for the Dark Energy Spectroscopic Instrument (DESI), an ambitious new instrument for the Kitt Peak Mayall telescope that will have 5000 robotic fiber positioners that feed light into ten bench-mounted, three-channel spectrographs. When complete in 2019, DESI will begin a five-year survey of over 35 million galaxies and quasars to better understand the nature of cosmic acceleration.