Materials that transition between metal and insulator, the two main states that distinguish all solids, are fascinating because they underlie many mysteries at the frontier of solid-state physics. In 1T-TaS2, the metal-insulator transition is linked to a metastable hidden state arising within a chiral charge density wave (CDW) whose basic nature remains an open question. In this talk, I will show that pulses of current through these materials create current-carrying filamentary channels that distinguish the ‘metallic’ hidden state and ‘insulating’ CDW states. These channels have remained dark to previous measurements and yet are directly linked to the properties of the hidden state. We leverage the metastability of these conduction channels to demonstrate electrical control of their creation, erasure and location. Our findings show that physical elements, such as boundaries and interfaces, play a key role in the properties of the hidden state characterizing the metal-insulator transition. We suggest new possibilities for in-situ electrical design of synaptic components with possible applications to neuromorphic computing.