The 20th century was a century that began on January 1, 1901 and ended on December 31, 2000. It was the tenth and final century of the 2nd millennium. It is distinct from the century known as the 1900s (sometimes written as 19XX), which began on January 1, 1900 and ended on December 31, 1999. The century in human history was dominated by World War I and World War II, nationalism and decolonization, the Cold War and Post-Cold War conflicts, cultural homogenization through developments in transportation and communications technology, world population growth, awareness of environmental degradation, and the birth of the Digital Revolution. It saw great advances in communication and medical technology that by the late 1980s allowed for near-instantaneous worldwide computer communication and direct genetic modification of plant, animal and human life.