It is still an open question as to whether anti-matter falls up or down - e.g. negative gravitational mass. The ALPHA experiment is using anti-hydrogen at CERN

It is still an open question as to whether anti-matter falls up or down - e.g. negative gravitational mass. The ALPHA experiment is using anti-hydrogen at CERN to find out. https://www.nature.com/articles/ncomms2787 https://www.nature.com/articles/ncomms2787 So far they have made some, but not enough to rule out experimental error.