  Intravital microscopy is an essential tool that reveals behaviours of live
cells under conditions close to natural physiological states. So far, although
various approaches for imaging cells in vivo have been proposed, most require
the use of labelling and also provide only qualitative imaging information.
Holographic imaging approach based on measuring the refractive index
distributions of cells, however, circumvent these problems and offer
quantitative and label-free imaging capability. Here, we demonstrate in vivo
two- and three-dimensional holographic imaging of circulating blood cells in
intact microcapillaries of live mice. The measured refractive index
distributions of blood cells provide morphological and biochemical properties
including three-dimensional cell shape, haemoglobin concentration, and
haemoglobin contents at the individual cell level. With the present method,
alterations in blood flow dynamics in live healthy and sepsis-model mouse were
also investigated.
