The invention comprises method and apparatus for fluid delivery between a sample probe and a sample. The fluid delivery system includes: a fluid reservoir, a delivery channel, a manifold or plenum, a channel or moat, a groove, and/or a dendritic pathway to deliver a thin and distributed layer of a fluid to a sample probe head and/or to a sample site. The fluid delivery system reduces sampling errors due to mechanical tissue distortion, specular reflectance, probe placement, and/or mechanically induced sample site stress/strain associated with optical sampling of the sample.