Metaphase

Metaphase came from the Greek μετα meaning "after." After the microtubules have found and attached to the kinetochores in prometaphase, the two centrosomes start pulling the chromosomes through their attached centromeres towards the two ends of the cell. As a result, the chromosomes come under longitudinal tension from the two ends of the cell. The centromeres of the chromosomes, in some sense, convene along the metaphase plate or equatorial plane, an imaginary line that is right in between the two centrosome poles. This line is called the spindle equator. This even alignment is due to the counterbalance of the pulling powers generated by the opposing kinetochores, analogous to a tug-of-war between people of equal strength. In certain types of cells, chromosomes do not line up at the metaphase plate and instead move back and forth between the poles randomly, only roughly lining up along the midline.
Because proper chromosome separation requires that every kinetochore be attached to a bundle of microtubules (spindle fibres), it is thought that unattached kinetochores generate a signal to prevent premature progression to anaphase without all chromosomes being aligned. The signal creates the mitotic spindle checkpoint.