Overview · What is this?
Cell division is how one cell becomes two — the process behind growth, healing a cut, and replacing worn-out cells. Every division starts the same way: the cell copies all of its DNA, then has to split that copy evenly between two new cells.
Mitosis is the everyday version: one cell splits into two identical daughter cells, each with a full, exact copy of the DNA. Meiosis is different — it's only used to make eggs and sperm. It divides twice in a row, mixes genes between chromosome pairs along the way, and ends with four cells that each carry only half the usual DNA, so a sperm and an egg can combine into a full set.
The machinery that actually pulls the chromosomes apart is the spindle — the fiber structure you're looking at. Scrub through the phases below to watch it build, grab each chromosome, and haul the copies to opposite ends of the cell. Try "Spot the error" to see what happens when that handoff goes wrong.