microns in thickness and this is still the standard technique for histology or standard pathology analysis so what I call the penetration limit in this case is the operation right so the way from distortion in order to form a very good image you have to have a very regular wavefront you have you have a controlled wavefront so in tissue because of the distribution of the refractive index in other words the speed of light will travel this light will travel at different speeds of light depending on which part of the