6 sentences

1. 猎户座星云用肉眼就能看见。

   Liè​hù​zuò xīng​yún yòng ròu​yǎn jiù néng kàn​jiàn.

   The Orion Nebula is visible to the naked eye.

   Source: Dong Chinese Dictionary

2. 这些细菌微小到肉眼看不见。

   zhè​xiē xì​jūn wēi​xiǎo dào ròu​yǎn kàn​bu​jiàn.

   These bacteria are so tiny that they are invisible to the naked eye.

   Source: Dong Chinese Dictionary

3. 成年人较难相信肉眼看不到的事物。

   chéng​nián​rén jiào nán xiāng​xìn ròu​yǎn kàn bù dào de shì​wù.

   Adults have a harder time believing in things they can't see.

   Source: OpenSubtitles

4. 由于距离遥远，肉眼很难观测到海王星。

   yóu​yú jù​lí yáo​yuǎn, ròu​yǎn hěn nán guān​cè dào Hǎi​wáng​xīng.

   It is difficult to see Neptune with the naked eye because it is so far away.

   Source: Dong Chinese Dictionary

5. 空气中悬浮着许多肉眼看不见的微粒。

   kōng​qì zhōng xuán​fú zhe xǔ​duō ròu​yǎn kàn​bu​jiàn de wēi​lì.

   Many particles invisible to the naked eye are suspended in the air.

   Source: Dong Chinese Dictionary

6. 凡夫肉眼，不识真金。

   fán​fū ròu​yǎn, bù shí zhēn​jīn.

   Ordinary mortals cannot recognize true worth.

   Source: Dong Chinese Dictionary