Dutch artist Johannes Vermeer (1632-1675) is among the most admired painters of his era. His most well-known work, Girl with a Pearl Earring, has even been nicknamed the "Dutch Mona Lisa." But Vermeer completed surprisingly few pieces — no more than 60 in total — during his lifetime, only 36 of which are still around. A recent discovery by the National Gallery of Art (NGA) in Washington, DC, has reduced the already paltry number even further.