Physicists and mathematicians have been working with archaeologists for years, collecting cosmic rays on all sides of the Pyramids and from all directions. If there’s less blockage in any particular area, it can be detected by analyzing cosmic rays coming through that area from all directions.
Today it was announced in a Nature article that they found a new passageway, about 10 M long beginning at a site where there is a known archway visible from the outside of the stones. A robot was sent in through a tiny opening to take pictures.
It may be a new chamber, previously unknown. Or it may be an architectural feature, directing the weight of stones above to the left and right so that it doesn’t crash the roof of a chamber below.