The brain transitions through distinct states of activity many times each second. These brain “microstate” sequences can be characterized using recordings of brain electrical activity (EEG), which reflects neuronal coordination at millisecond time-scales relevant for human cognition. Ongoing perceptions, thoughts, and experiences are presumed to depend on the coordinated activity of brain networks at this sub-second level, but methods linking the activity of synchronized brain states to spontaneous felt experience have been limited. As such, the goal of the present study is to utilize first-person experiential reports to guide an investigation of millisecond brain microstate dynamics. Study participants will utilize structured questions to guide introspection about the content and quality of their ongoing thoughts and experiences while they sit quietly with eyes closed. Simultaneous EEG will be recorded and microstates will be characterized in the ongoing EEG, and associations between individuals’ brain microstate dynamics and self-report will be examined. A key question this study will answer is whether microstate dynamics fluctuate alongside individuals’ thoughts and felt experiences. This study will shed light on the mechanisms by which sequences of coordinated brain states enact one’s rich and complex phenomenal experiences, and guide future neurophenomenological studies of microstates.