A microscope comes with an objective of 10X (low power) 45X (high power) and 100X (oil immersion). and the ocular lens with 5X, 10X and 15X. In general, an 10-X ocular lens is used in most cases. If an animal can be clearly seen with 10X ocular lens and 45X objective, this means that the size is 10×45, which is 450 times larger than the standard one. We don’t know the exact measurement is ? It could be determined using an calibrated scale. Thus the calibration of all lenses (eyepieces) is performed.