Their first significant 20th-century purchases were two Fontanas a work on paper and a white painting which they selected with the help of James Kelly, a Santa Fe gallerist they've been working with since 1999.

WSJ: The House That Gucci Built

The Rothko painting was one of eight works hand-selected by the Russian-American artist for his landmark solo show in 1954 at the Art Institute of Chicago.

BBC: Mark Rothko painting crowns New York art sale

When you have selected the type of scientific study of a painting or sketch, a simple slider movement left or right takes you on an X-ray journey through one of the master's works.

BBC: 8bitpeoples

Da Vinci might have selected different glaze recipes on purpose or he may have tweaked the painting over years during which time his taste in glaze ingredients could have changed.

ECONOMIST: The da Vinci method