Cosmology is the part of astronomy that specifically examines the origin of the universe. Until the advent of modern astronomy, cosmology was relegated to the domain of religion or abstract philosophy. Today, cosmology is a vibrant part of science and is not limited to gazing out into the cosmos. Current scientific theories have shown that the universe was once far smaller than an atomic nucleus. This means that modern particle physics and high-energy physics, which can be studied on Earth, are absolutely necessary to decipher the mysteries of the very early universe and, ultimately, the very beginning of everything.