The Cryogenian Period is a geological time frame that lasted from about 720 to 635 million years ago. It is known for its extreme ice ages, during which the Earth experienced significant glaciation. These ice ages are believed to have covered much of the planet, possibly even reaching the equator, leading to the term "Snowball Earth." During the Cryogenian, the planet's climate fluctuated, and the ice eventually began to melt, paving the way for the emergence of more complex life forms. This period is crucial for understanding the evolution of early multicellular organisms, setting the stage for the subsequent Ediacaran Period and the Cambrian explosion of life.