  Chirality is essential for various amazing phenomena in life and matter.
However,chirality and its switching in electronic superlattices, such as charge
density wave(CDW) arrays, remain elusive. In this study, we characterize the
chirality transition with atom-resolution imaging in a single-layer NbSe2 CDW
pattern by technique of scanning tunneling microscopy. The atomic lattice of
the CDW array is found continuous and intact although its chirality is
switched. Several intermediate states are tracked by time-resolved imaging,
revealing the fast and dynamic chirality transition. Importantly, the switching
is reversibly realized with an external electric-field. Our findings unveil the
delicate transition process of chiral CDW array in a 2D crystal down to the
atomic scale and may be applicable for future nanoscale devices.
