What are some of the most interesting little-known things?

1.The pleasant smell of first rain after a long time (called petrichor) is actually due to geosmin produced by bacteria present in wet soil. It is also attributed to an oil released by plants to keep themselves from drying out.

(Ok, I hear some mild cursing. Sorry for sucking out the romance.)

(image from bird and moon)

2. 3D printers today can print clothing, houses, lenses, food, body parts and 3D printers also.[2]

Below is a 3d printed working human ear.

(What follows one might initially find it creepy, but bear with me)

3d printing can be used to print sonograms i.e. life size developing babies. These 3D sonograms are used to help blind expectant parents "see" their babies.[3]

3. A drop of liquid can be held up by its vapour if its in touch with a hot surface.(Leidenfrost effect)

Due to this effect some people have stuck their hands in liquid nitrogen and have taken it out unscathed.

WARNING: DON'T DO IT AT HOME. DIRECT CONTACT WITH LIQUID NITROGEN CAN CAUSE IRREPARABLE DAMAGE.

4. Up until the mid-15th century, all children were referred to as girls. Boys were called "knave girls" and girls were called "gay girls". Previously the word boy, meant a servant.[4]

5. The brain does not feel pain because there are no pain receptors in the brain. Therefore, surgeons can perform brain surgery on awake patients.

The brain tissue itself is not sensitive to pain because it lacks pain receptors(nociceptors). The pain during a headache is caused by disturbance of the pain-sensitive structures around the brain.[5]

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[1]Petrichor
[2] 10 Incredible Things You Can Make With 3D Printers - Listverse
[3] 3D sonograms let blind expectant parents "see" their babies
[4] QI (G series)
[5] Headache

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