How Do You Distinguish Between Different Asians?

I mean, how do you tell Koreans, Chinese, Japanese, Vietnamese, Indians, Cambodians, and the others apart. I'm not talking about the Pakistan part of Asia. I know that they all have different traits. I'm Vietnamese, but My family is very mixed. Some of us are pale, some are tanned, some have big eyes, and others have chinky eyes. My skin tone is in the middle of tan and pale, but more tan. and my eyes are large compared to other Asians, and I am tall for a Viet. But my sister is pale with chinky eyes and is super short, and my brother has chinky eyes, but is tan. So, how Do you tell all the Asians apart? I don't want answers like "Because they are" or "You should know. Youre asian" Pleas give me everything you know about this. Thank you!