We all have that friend who prefers spending Saturdays 3D-printing stuff. Maybe you have a buddy who can't stop picking out inconsistencies in Interstellar. Or, someone who would like nothing more than to be left alone with a book of Victorian medical illustrations. We've all got at least one fabulous science nerd in our lives.
We love them dearly, but these people's varied interests and fickle tastes are very difficult to shop for. So, what do you get the mad scientist in your life?