The rodent's primary somatosensory cortex (S1) processes sensory information from the whiskers on the snout. During active sensation, cortical pyramidal neurons integrate feedforward and a variety of feedback inputs to form a percept. In S1, feedback input from the higher-order (HO) posteromedial thalamic complex (POm) was shown to facilitate NMDAR-mediated nonlinear dendritic events in L2/3 neurons, which enhance synaptic plasticity and promote spiking. Such events greatly depend on the spatial and temporal arrangement of synaptic activity. However, the spatiotemporal relationship between HO thalamic feedback and the sensory-related synaptic inputs onto L2/3 neurons is not understood.Here, we developed a novel methodological pipeline that allows the identification of active synaptic connections in vivo with high spatiotemporal precision. The method combines the expression of a presynaptic light-sensitive opsin in axonal afferents to optically activate long-range thalamocortical or corticortical projections to S1, with a postsynaptic genetically encoded glutamate indicator to visualize the activated excitatory synapses. Proof of principle experiments indicate that we can specifically visualize the location of synapses from long-range projections as well as those activated by sensory stimuli on pyramidal neurons. Furthermore, we investigated the spatiotemporal relationship, synaptic properties, and rearrangements of synaptic connectivity between long-range and sensory-driven synaptic inputs onto S1 pyramidal neurons over multiple days.