个个 / 天天 / 人人【gègè / tiāntiān / rénrén】

Doubling a one-syllable measure word gives "every single one". The doubled word sits before the verb, and 都 almost always follows it.

A few nouns that work like measure words double the same way: 人人 "everyone", 家家 "every household", 天天 "every day", 年年 "every year".

天天 or 每天

The doubled form is more emphatic and a little more colloquial than 每 + measure word: 天天 stresses that not one day is missed.

Before the verb, never after

The doubled measure word is a subject or a topic. It can't stand as the object after the verb, so the thing being counted moves to the front.

• × 我喜欢件件衣服 → 这些衣服我件件都喜欢
• × 我认识个个学生 → 这些学生我个个都认识

Only one-syllable measure words double this way. With 一 in front, 一个个 or 一个一个 means "one by one", which is a different pattern.