改天换地 change the world
Explanation
彻底改变原来的面貌。比喻变化巨大，使天下改观。
To thoroughly change the original appearance. It is used to describe a huge change that changes the world.
Origin Story
很久以前，在一个偏远的山村里，生活着勤劳朴实的村民们。他们世世代代生活在贫瘠的土地上，过着日出而作，日落而息的简单生活。村里只有一条狭窄的土路，通往外面的世界。然而，这条路崎岖不平，每逢下雨就泥泞不堪，村民们出行十分不便。 有一天，一位年轻的工程师来到这个村庄。他看到村民们如此艰苦的生活，决心帮助他们改变现状。他首先带领村民们修建了一条宽阔平坦的水泥路，方便了村民们的出行。接着，他又帮助村民们引进了新的农业技术，提高了农作物的产量。他还帮助村民们建立了一个小型的水电站，解决了村里的用电问题。 经过几年的努力，这个小山村发生了翻天覆地的变化。宽阔的柏油路连接着家家户户，村民们住上了明亮舒适的房子，孩子们在宽敞明亮的学校里学习，村里的生活水平得到了极大的提高。曾经贫瘠的土地上，如今长满了茂盛的庄稼，村民们脸上洋溢着幸福的笑容。这个小山村，已经从一个落后的山村，变成了一个欣欣向荣的现代化村庄。
Long ago, in a remote mountain village, lived diligent and simple villagers. They lived on barren land for generations, leading a simple life from sunrise to sunset. There was only a narrow dirt road leading to the outside world. However, this road was rough and impassable, and became a swamp when it rained, making it very inconvenient for the villagers to travel. One day, a young engineer came to this village. Seeing the villagers' difficult lives, he decided to help them change their situation. He first led the villagers to build a wide and flat cement road to facilitate their travel. Then, he helped the villagers introduce new agricultural techniques to improve crop yields. He also helped the villagers build a small hydroelectric power station to solve the village's electricity problem. After years of hard work, this small mountain village underwent a dramatic change. Wide asphalt roads connected every household, villagers moved into bright and comfortable houses, children studied in spacious and bright schools, and the village's living standards greatly improved. On the once barren land, lush crops now grew, and the villagers' faces beamed with happiness. This small mountain village has transformed from a backward mountain village into a thriving modern village.
Usage
形容变化巨大，彻底改变原有的面貌。常用于政治、社会、自然等领域。
Describes a huge change that completely changes the original appearance. Often used in the fields of politics, society, and nature.
Examples
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这场改革，真是改天换地，令人刮目相看。
zhè chǎng gǎigé zhēnshi gǎi tiān huàn dì, lìng rén guā mù xiāng kàn.
This reform has really changed the world and is admirable.
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经过几年的努力，家乡的面貌已经改天换地了。
jīngguò jǐ nián de nǔlì, jiāxiāng de miànmào yǐjīng gǎi tiān huàn dì le
After a few years of hard work, the face of my hometown has changed dramatically.