Spindle fibers are protein structures that form early in mitosis, or cell division. They consist of microtubules that originate from the centrioles, two wheel-shaped bodies located in the centromere area of the cell. The centromere is also known as the microtubule organizing center.
1 Night terrors are characterized by frequent recurrent episodes of intense crying and fear during sleep, with difficulty arousing the child. Night terrors are frightening episodes that disrupt family life.  A small percentage of children experience night terrors.
Night terrors are relatively rare â they happen in only 3â6% of kids, while almost every child will have a nightmare occasionally. Night terrors usually occur between the ages of 4 and 12, but have been reported in kids as young as 18 months. They seem to be a little more common among boys.