We present a small headstage for multichannel neural recording and optogenetics stimulation designed for freely moving laboratory mice. The headstage incorporates a new 0.13-µm system-on-chip (SoC) featuring all the circuitry for performing multichannel optogenetic stimulation and multichannel brain recording. The SoC has 10 multimodal recording channels and a 2-ch LED drivers. Digitization is done using in-channel Delta-Sigma MASH 2-1 ADC with on-chip decimation. The headstage incorporates a Bluetooth-low-energy (BLE) transceiver along with a Cortex-M4 processor. The system weights 1.24 g with the battery (0.5 g w/o battery), has an autonomy of 150 minutes, and occupies a volume of 0.65 cm³, making it the smallest electro-optic devices for freely moving brain research. We report in vivo results obtained in the hippocampus brain region of a mouse.