With Groat's stain, the type I collagen stains green, so the newly formed bone stands out nicely. This image of a section of the fetal skull shows both intramembranous (HA8, right) and endochondral ossification (HA8, left). Although the purpose of this image is to study intramembranous ossification, notice how the bony collar is being formed around the hyaline cartilage model in this early stage of endochondral ossification of the occipital bone of the skull.