This study is to find out whether and how a type of non-invasive electrical brain stimulation called transcranial electrical stimulation with temporal interference (TES-TI) can temporarily change brain activity in healthy adults. A structural MRI scan will be used to customize where the stimulation electrodes are placed for each participant to deliver TES-TI during three afternoon sessions at rest with eyes closed. Brain activity is recorded with high-density EEG. Up to 24 participants will be enrolled and on study for 3 to 12 weeks.