These are the best popular science videos of last week:
AsapSCIENCE: why do we cry?
SciShow: present and future of 3D printing, including printing of organs! (And there's also this TED talk about printing human kidneys.)
TEDTalks: deep brain stimulation to cure Parkinson's disease, Alzheimer's disease, and depression too.
TED-Ed: how do particle accelerators work?
MinuteEarth: the invasion of bed bugs.
Mental Floss: 31 famous people marrying their cousins.
Vsause: how big can a person get?