Here's a great talk by Letizia Treves, the Curator of Italian and Spanish Paintings 1600-1800, National Gallery of London.
It's on Caravaggio, and is one of their series of lunchtime talks, and lasts about half an hour.
It's really good, so enjoy!
Caravaggio, Boy Bitten by a Lizard (Oil on canvas, 1596)
Caravaggio, Supper at Emmaus, Oil on canvas 1602
Caravaggio, Salome with the Head of John the Baptist (Oil on canvas, 1607)