It’s a huge moment in the world of science: four new elements have been added to the periodic table, completing the seventh row.

They were added by the International Union of Pure and Applied Chemistry (IUPAC). Elements 113, 115, 117, and 118 were all added, the first time an addition has been made to the table since 2011, according to a Huffington Post report.

And they are some fascinating elements. For one thing, they are entirely man-made, and are also super-heavy.

The RIKEN institute in Japan discovered Element 113, which is called unutrium with the symbol Uut. Scientists at the Joint Institute for Nuclear Research in Russia, the Lawrence Livermore National Laboratory in California, and the Oak Ridge National Laboratory in Tennessee found Elements 115 and 117, which are called ununpentium (Uup) and ununseptium (Uus), respectively. The last element, Element 118, was discovered by both the Russian and California teams, and it is called ununoctium (Uuo).

The names of the elements may change. The IUPAC allows the discoverers of these new elements to decide on a permanent name or symbol over the next few months, although they are limited to what they can name it after. Generally, it’s restricted to places, scientists, or mythological concepts.

How did scientists discover these elements? They smashed lighter nuclei into each other, and then analyzed the radioactive decay afterward. It too a decade of work to recognize the element.

The scientific teams don’t plan to stop there, and will look for Element 119 and beyond.

Completing the seventh row was a big deal for the chemistry community.

“The chemistry community is eager to see its most cherished table finally being completed down to the seventh row,” said Professor Jan Reedijk, President of the Inorganic Chemistry Division of IUPAC, in a news release. “IUPAC has now initiated the process of formalizing names and symbols for these elements temporarily named as ununtrium, (Uut or element 113), ununpentium (Uup, element 115), ununseptium (Uus, element 117), and ununoctium (Uuo, element 118).”