顧名思義，異卵雙胞是由兩條精子分別與兩粒卵子結合而來，兩個胚胎各自帶著不同的遺傳基因，兩個胎兒的性別也不一定相同；一男一女的「龍鳳胎」就是異卵雙胞胎了。

雙胞胎可分為兩大類：異卵雙胞和同卵雙胞。

異卵雙胞胎 Fraternal twins

通常被人们称为假双胞胎”。

即使是相同性別，異卵雙胞的「孖仔/孖女」外貌也不會完全一樣。

異卵雙胞的胎盤屬於雙絨毛膜雙羊膜類，每個胎兒均有獨立的絨毛膜和羊膜；意思是在媽媽的子宮內，兩個胎兒各自有「獨立的房間」，所以他們互相干預的機會很低。

同卵雙胞胎 Identical twins

同卵雙胞則是由一條精子與一粒卵子結合而來，受精後的胚胎一分為二，分裂出來的兩個胚胎有相同的遺傳基因，兩個胎兒的性別也相同，一定不是「龍鳳胎」。

即他们具有相同的基因，所以出生后的双胞胎性别相同、容貌相似，血型、体质等也相同，这通常被人们称为真双胞胎”。

同卵雙胞的「孖仔/孖女」外貌會完全一樣。同卵雙胞的胎盤類型又可細分為雙絨毛膜雙羊膜、單絨毛膜雙羊膜或單絨毛膜單羊膜三種。

單絨毛膜單羊膜類是最危險的，因為這類雙胞胎的兩個胎兒沒有羊膜分隔，在媽媽的子宮內沒有「獨立房間」，所以他們「打架」或互相干預的機會較大。他們的臍帶可能會纏結，導致缺氧。最極端的狀況就是聯體孖胎，俗稱「連體嬰」。

單絨毛膜雙羊膜類的雙胞胎，則會出現雙胎輸血症的風險，其中一個胎兒會搶去另一胎兒的血液。

18%的同卵雙胞胎有不同的優勢手：比如哥哥擅長左手，弟弟可能擅長右手。

雙胞胎會有相同的指紋嗎？ 其實對於雙胞胎來說，他們可以有一樣的臉、一樣的生日、性格、甚至DNA，但是相同的指紋是少之又少，但是生命總會有奇蹟，說不定世界上某個角落會有相同指紋的雙胞胎，只是這種概率非常之小。

雙胞胎會有自己的語言嗎？ 答案是會的。 科學表明，雙胞胎之間會有自己獨特的語言和交流方式，並且父母是無法破譯的。

幾乎一半的雙胞胎都有自己的語言：為了相互交流，大約40%的雙胞胎創造了一種只有他們自己理解的語言。

雙胞胎會有不同的生日嗎？ 會有不同生日的雙胞胎。 比如第一個寶寶在23：59出生，而另一個在第二天的0:00出生，這就擁有不同的生日啦！

雙胞胎有心電感應嗎? 答案是有的!

mental telepathy 心電感應 心電感應的天賦是否存在這些人的潛意識中，和所傳達的訊息可以被儲存並且由光子傳輸給對方．在雙胞胎的實驗當中，許多系列的測試已非常清楚證明此類的兄弟可以相互溝通，而溝通的方式卻無法以正統物理學去加以解釋的，雙胞胎有著完全相同的遺傳因子，很明顯地會大大增加心電感應的技巧。

實事上，縱然感受不是很強烈但我們每天的日常生活亦會有心電感應的感覺

一對雙胞胎被分離在不同的孤兒院彼此互不認識，卻試圖著和對方聯繫而終於找到對方，特別是在雙胞胎其中一位遭遇到危急狀態時，心電感應的潛在力量非常戲劇性的被發揮出來．

個人例子: 在我幼稚園的時候,有一次我開開心心和其他小朋友玩玩具莫名其妙突然大哭,老師也百思不得其解...後來老師問我我只說我要找妹妹,老師帶我到妹妹的班級,發現妹妹一直哭。 我哭因為妹妹在哭。

爸媽不同種族的話，雙胞胎看起來像是不同種族的機會只有百萬分之一

夫妻 Remi Horder 和 Kylee Hodgson 真的就有一對這樣的雙胞胎寶寶。Kian 是黑皮膚、深咖啡色頭髮、深咖啡色眼珠，但是 Remee 是白皮膚、金頭髮、藍眼珠。

從綜合研究結果看起來，同卵雙胞胎一起出櫃的機會大約在五成左右，而異卵雙胞胎性傾向的相關性就比較低，降到兩成左右；也就是說，當異卵雙胞胎的其中一個出櫃時，另一位也出櫃的機會大約20%左右。

基因愈相同，性傾向愈一致

Imagination will often carry us to worlds that never were. But without it we go nowhere.

I have a fascination for extra-judicial societies and underground cultures, and in situations where justice can only be found outside the law, and how these societies have evolved over the centuries.

I try to only read light things when I'm working on my books, and in the evenings I watch a lot of mindless TV. I have to break up the 'dark,' or I wouldn't be a very happy person.

I have not missed a day from work because of illness since 1956.

If there's a British film in the marketplace that is successful on a worldwide basis - whether it's 'A Room with a View,' 'Four Weddings' or 'The Full Monty' - money follows, and everyone tries to emulate that success.

There was a boy in my building who was my best friend when I was growing up. There was also a mysterious person on my corner who we called the Laughing Man.

When you are surrounded by children, the child in you comes back.

Bad things happen when you try to let things just happen. You can't be passive.

I am tired, beloved, of chafing my heart against the want of you; of squeezing it into little ink drops, and posting it. And I scald alone, here, under the fire of the great moon.

I like to tell stories through dancing and singing.

Teofilo Stevenson won his first Olympic gold medal in 1972 and his last world amateur championship in 1986. He won 302 fights and once went an unbelievable 11 years without a loss. Had Cuba not boycotted the 1984 Summer Olympics, many think Stevenson would have won an unmatched four gold medals in boxing.

Faith is much better than belief. Belief is when someone else does the thinking.

Tradition can, to be sure, participate in a creation, but it can no longer be creative itself.

My friends call me a 'pace-setter.' Sometimes I am impatient, I think, but you must be fast and flexible in business because uncertainty is the only certainty in life.

My love of maple syrup. I've been known to knock back a can over a couple days: A swig here, a swig there, and next thing you know it's gone. It's a habit I have to stave off. I don't want to lose all my teeth.

I did 'The Grey,' and it was very intense and emotional because we're in the wilderness, and it was always 30 degrees. You kind of lose your sense of reality in the fact that you're filming a movie.

The idea that you earn things - that you earn respect, that you earn income, responsibility. the vote, punishment... these ideas are anathema to the liberal mind.

It seems to me if you don't know anything about child development you shouldn't intimate in your 'reporting' that you do.

I liked a lot of the things other people liked - Jimi Hendrix, The Beatles, Van Halen, AC/DC - but if I compared it to my dad's music, there just seemed to be elements missing.

Know that there is enough for all of us - enough money, enough opportunity, enough love for all of us to be happy.

The beauty of standing up for your rights is others see you standing and stand up as well.

I usually start writing a novel that I then abandon. When I say abandon, I don't think any writer ever abandons anything that they regard as even a half-good sentence. So you recycle. I mean, I can hang on to a sentence for several years and then put it into a book that's completely different from the one it started in.

If our system of cabinet government is to work effectively, the prime minister of the day must appoint ministers he or she trusts and then leave them to carry out that policy.