Liu at.al published their results in Nature Communications using NeuroNexus A4x8-5mm microelectrode arrays. Single neuron recordings were captured during optogenetic stimulation with blue, green and red light emitted by trichromatic upcoversion nanoparticles with excitation-specific luminescence. They showed the separation of blue, green, and red color emissions by measuring the spike activity of multiple neuronal populations under selective activation with different wavelengths of near infrared light.