When it comes to little-known facts, people probably think of some obscure and strange things, but few people pay attention to these little-known facts because they may not be of much use. Today, let's take a look at 21 little-known facts: facts that exist but are rare, and many people may find them strange.

1. The human lungs are actually quite large; if the entire lung were opened, its size would be roughly equivalent to that of a normal tennis court.

2. Many people may not know that babies actually dream during pregnancy, even though they haven't seen the outside world.

3. If sheep eat curry, it can reduce the methane content in their farts by about 40%.

4. Some older people want to eat meat but find it difficult to digest. They can try eating vegetables first, then eating meat, as this will make it easier to digest.

5. People often catch colds during seasonal changes. Some young people, not wanting to delay things, will simply buy some cold medicine. But did you know that cold medicine doesn't cure a cold? Cold medicine only relieves symptoms; it's the body's immune system that heals a cold.

6. Koi not only bring good luck, but they also have a long lifespan; if raised well, they can live almost as long as humans.

7. There are many acupoints on the human body, each corresponding to a specific organ. To improve brain agility and intelligence, try stimulating the acupoints on the ears.

8. In ancient times, the deceased were highly respected. The phrase "three long and two short" (三长两短) has a negative connotation nowadays, and the shape of a coffin is also associated with this.

9. The hospital previously stipulated that medical orders must be written with blue ink because ferrous tannate is present in the ink, allowing for the determination of the writing time. This was also to prevent unscrupulous individuals from exploiting loopholes.

10. Do you like cilantro? Experts say it might not be that you can't stand the taste of cilantro, but rather that it's due to your genes. Approximately 15% of people worldwide dislike cilantro.

11. Statistics show that frequent kissing between couples can help prevent skin from sagging and make it firmer. So ladies, hurry up and start kissing your husbands!

12. Do you eat late-night snacks? Data shows that the urge to eat at night is often due to loneliness. If you had a family, you would be resting earlier.

13. A survey specifically targeting middle-aged and elderly people showed that some elderly people who have a habit of taking a nap do not look very old.

14. If your body is calcium deficient, there's a natural calcium supplement: eggshells. Eating them will help you get calcium. However, many calcium supplements are available now, so this is an old-fashioned method.

15. To extend the lifespan of rubber bands, try placing them in the refrigerator when not in use; you'll find they last much longer.

16. Cape Helena in South America is also the closest place to Antarctica. Due to natural factors, the ozone layer is severely damaged, and ultraviolet radiation is excessive, making it difficult for many animals to see clearly.

17. I'm sure you've all seen videos of groundhogs online. Not only are their squeaks hilarious, but it's even more entertaining to see two groundhogs fighting.

18. If you are balding, there is a treatment, but I don't know if you know the "Sunflower Manual" (a popular Chinese medical text), that's right, castration. Hair loss is caused by a lack of dihydrotestosterone (DHT).

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20. Girls who love beauty love to apply nail polish, but after applying it, they need to use a machine to dry it. If you don't have a machine, you can try putting it in cold water, which will also make it dry quickly.

21. Beverages are practically a must-have for young people these days, but did you know that drinking beverages with a straw can effectively prevent tooth decay?

22. As living conditions have improved, meat is practically a staple at every meal. However, if you eat something too greasy, drinking tea afterward can promote fat metabolism and aid digestion.

23. A girl's jewelry is very precious. You can put a small piece of chalk in the jewelry box to make the jewelry shine.

24. If you've eaten strong-smelling foods like chives, garlic, snail rice noodles, or stinky tofu, and you don't want your mouth to smell, try eating a few peanuts. It will help a lot.