Supermarkets have lots of milks to choose from these days, many of which are the product

of blending up and straining various nuts and seeds.

Plain old milk milk, on the other hand, is also a strained product - it's filtered

cow blood.

As weird as this seems, all mammal milk is, in fact, made from blood, because blood contains

lots of nutrients, and baby mammals need lots of sugar, fat, and protein to grow complex

brains and bodies.

But mammal mammas can't just open an artery; that would be dangerous.

Plus, most of the useful nutrients in blood are too dilute and blood has too much iron

for most babies to process.

This is where the mammary gland comes in: It's full of thousands of tiny sacs whose

walls have special cells that grab water and nutrients from passing blood, do some chemistry

on them, and pass them to the inside of the sacs where they mix together to become milk.

When a baby starts to suckle on the teat, its sucking pattern tells the mom's brain

to the hormone release oxytocin, which attaches to the sacs, causing them to squeeze out the

tiny droplets of milk into the baby's mouth.

Each mammal species tailors its blood-filtering recipe to the needs of its babies.

For example, to help their Arctic-dwelling pups pack on the blubber, hooded seal moms

produce a milk with 15 times the fat of cow milk.

Cottontail moms make high-protein milk for their bunny babies, allowing them to develop

their hopping muscles quickly.

The tammar wallaby can make two different types of milk in two different teats at the

same time - one high in sugars for a newborn in the pouch and one high in fat and protein

for her waddler.

And while selectively bred modern dairy cows don't have a particularly wacky recipe for

their milk, they sure make a lot of it.

The current record holder - a Holstein named Aftershock - can produce a bathtub full of

milk every day.

That's udderly impressive.

This video is sponsored by Honey, a free browser extension that looks for ways to save you

money whenever you shop online.

You can install Honey with just two clicks of the mouse by going to joinhoney.com/minuteearth.

After that, any time you go through the checkout process at an online store, Honey will automatically

apply the best coupon code it can find to give you the biggest discount.

Last week, the MinuteEarth team saved seven bucks on this amazing chart of cosmic exploration

from PopChartLab.

And Honey doesn't make money by selling your personal data; instead, it collects a

small commission from some merchants for bringing them customers.

To join the nine million other people using Honey to save money online - and to support

our channel - go to joinhoney.com/minuteearth.