In order to apply scanning near-field optical microscopy to life science, it is essential to have an accurate distance feedback that also works on soft biological samples in liquids. In this letter, we report measurements of neuron cells in aqueous solution using an advanced piezoelectrical shear-force detection setup. Simultaneously obtained topographical and fluorescence images are presented, demonstrating a resolution below 100 nm in the optical image. The influence of the water level on the shear-force signal and the interaction between near-field probe and soft organic samples are discussed. Stable feedback in fluids is obtained with tip–sample interaction forces below 100 pN. ©1997 American Institute of Physics.