Imagine building a city with just two types of buildings: red homes and green offices. You spread the buildings out evenly, alternating red and green. Now, imagine that same city with neighborhoods and business districts. The 3-D map would have distinct areas of red and green. Dr. Xiao-Ying Yu at DOE’s Pacific Northwest National Laboratory and her colleagues ended up with a similar map when they delved into a popular solvent, known as a switchable ionic liquid, or SWIL. The team drew the first chemical map of a SWIL.