Most of our understanding of the brain activity and its relation to behavior comes from the electrophysiological studies of neuronal activity at different levels. Extracellular recording of spiking and local field potential activity gives the most comprehensive picture of the brain activity at the neuronal ensemble level within a region as well as across brain areas. Juxtacellular recording approach is best suited for investigating the activity of individual classes of neurons that are further characterized in relation to their morphology, molecular content, and axonal projection profile. Intracellular recordings uncover intrinsic and synaptic subthreshold dynamics of individual neurons that are not detectible using the other two techniques. Electrical and optical stimulation of neurons complements the recording techniques and are used to artificially control the neuronal activity with incredibly high temporal resolution. The current work reviews these four approaches for studying neuronal activity in vivo and provides an overview of the most recent advances and trends in this field.