A tesseract is a wrinkle in space and time that allows the Murry children, like their father before them, to leap over great distances in the space-time continuum. As Mrs. Whatsit explains it, if you wrinkle up the cloth of a skirt, an ant can travel across it much faster. Likewise, by using wrinkles in time, Mrs. Whatsit, Who and Which can almost instantly arrive at other planets. Tessering, or using a tesseract, allowed Mr. Murry to get quickly to the planet Camazotz, and it allows Meg, Charles Wallace and Calvin to follow him there and save him from the power of IT. It also allows all of them to return to earth in the blink of an eye. This fortunate feature makes space travel possible for humans.