Lipopolysaccharide (LPS, also known as endotoxin) in Gram-negative bacteria is critical for the bacterial survival and their resistance to antibiotics. As a critical step of LPS biosynthesis, newly produced LPS in the cytoplasmic leaflet of the inner membrane is flipped to the periplasmic leaflet by MsbA, an ATP-binding cassette transporter. In a recent study published in Nature on September 6, the Liao lab use single particle cryo-EM to obtain high-resolution snapshots of MsbA at different functional states. This study uncovers the structural basis for LPS transport, and paves the way for structural characterization of many other lipid flippases.