Researchers have grown atomically thin crystalline layers of transition metal dichalcogenides (TMDCs) with varying composition over space, continuously feeding in different types of TMDC to a growth chamber to tailor changes in properties. Examples include 20nm strips surrounded by different TMDCs with atomically straight interfaces, and layered structures. They also directly probed the electronic properties of these heterostructures; potential applications include electronics with unparalleled power efficiency.