Histological slides are typically very thin, usually around 5-10 micrometers, to allow for the passage of light through the tissue when viewed under a microscope. This thinness ensures that the sample is sufficiently transparent for detailed examination. Thicker sections would scatter light, reducing the clarity and detail of the image. Thin sections also ensure that cells and structures within the tissue are observed in a single plane of focus, providing a more accurate representation of the tissue's morphology.