The liquid microlayer under a small bubble for lowly-subcooled nucleate flow boiling of R113 is investigated using laser interferometry. The experimental errors and experimental technique are studied. The experiment results show: 1.Under the condition of lowly-subcooled nucleate flow boiling, there is usually a wedgelike microlayer beneath the bubble and the main flow has no influence on the miccrolayer. 2. At nucleation site, there is usually a dry spot beneath the bubble. 3. Once the bubble migrates, the dry spot disappears. The results are very important for the further analyses of the microlayer's influence on boiling heat transfer.