Turbo sizes

I'm trying to research how much I can turbo my b16a3 for in the future when I have the money. I'm looking for low end power as quickly off idle as possible so I want a small turbo that spools right away. What is the smallest size turbo available? How many sizes of turbos are there? A list of the different turbo sizes would be great if possible.

With any turbo you'll have some lag if you want low end get a S/C as far as the smallest i don't know probbly one off a mirco car in japan they have some 800cc motors with turbos the size of a soda cans and amount there alot

Well I know there's always gonna be lag but I'm not interested in a SC. I'm looking at brand name turbos like HKS, Greddy, or Garret. I see all the flange sized like T25 and T3/T4 but I don't know what those names refer to. Considering only normally used turbos what is the smallest size?

t25 is about the smallest you can go. very quick spooling.