Hydrogen exists as a gaseous compound of two hydrogen atoms (H2). Under normal laboratory conditions, H2 occurs in the variants "ortho hydrogen" and "para hydrogen." Until now, it has been unclear how these variants behave under very high pressure. Researchers at the University of Bayreuth have now found the answer. Both ortho- and para-hydrogen become unstable under high pressure and cease to exist as distinguishable states. The research results presented in Nature Communications extend our physical understanding of fundamental quantum mechanical processes.