The latest Objectivity video deals with two "death masks" stored at the Royal Society.
They are casts of the faces of two great men in the fields of maths, astronomy and physics.
Isaac Newton died in 1727 and James Jeans in 1946.
Newton's death mask is well-known - in fact I've filmed it before.
Newton's face was cast at time when such things were common.
For example, they were useful tools for sculptors making posthumous statues.
The mask spent many years in the Jeans home, but has now been entrusted to the Royal Society.
You can read more about it on the society blog.