The recent successful development of the helium ion microscope has produced both a new type of microscopy and a new tool for nanoscale manufacturing. This chapter reviews the first explorations in this new field in nanofabrication. The studies that utilize the Orion helium ion microscope to grow or remove material are described, concentrating on helium ion beam deposition, milling, and etching. Helium ion beam induced deposition combines the advantage of electron beam deposition, namely high spatial resolution, with that of heavy-ion beam induced deposition, namely high efficiency. Helium milling is much slower than gallium milling, but ideal for structuring thin slabs of material with high precision. A handful of studies has demonstrated the possibility of helium ion beam etching. Experimental and theoretical studies suggest that secondary electron emission is the dominant mechanism in helium ion beam induced processing.