Optical approaches to image and modulate brain activity are limited in their penetration depth in live animals, owing to the strong scattering and absorption of photons in the visible spectrum. Carbon nanotubes and carbon-based polymers, in contrast, afford unique optical properties in the second near-infrared window (NIR-II window, 1000-1700 nm) with reduced scattering and absorption by the brain. In this talk, I will present my lab’s latest work on the imaging and modulation of brain activity with carbon nanotubes and carbon-based polymeric nanoparticles in the live mouse brain. Specifically, the NIR-II window enables through-scalp imaging of cerebrovasculature and modulation of deep-brain neural activity in freely behaving animals via a minimally invasive, implant-free, and tether-free optical interface. Our development of carbon- and polymer-based deep-brain imaging and neuromodulation has been published in Nature Photonics (2014), Nature Biomedical Engineering (2017), Nature Biomedical Engineering (2022), and ACS Nano (2023).