Dentinal tubules close to the dentino-enamel junction
This image shows dentinal tubules situated close to the dentino-enamel junction (DEJ), also known as as the amelo-dentinal junction. The diameter of the dentinal tubules is quite small and the tubules lie farther apart. There's also an erythrocyte in the image making it easier to get a grip on the size of a dentinal tubule. The diameter of a healthy erythrocytes is about 7,5 µm.
Compare this image to another electron microscopic image of dentinal tubules showing a wider diameter.