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?

Playlist