What is the smallest crochet hook size available, and what type of yarn would you use to crochet with it?.. I am looking to crochet some mini amigurumi type things… I have used 100 % cotton worsted weight yarn up to this point , obviously that wont work for small hooks, but have no idea what to use.
Thanks!
Size 14 (.75mm) or size 15 or 16 (.4mm) if you can find them and size 100 crochet thread or sewing thread.
I tried a size 7 (1.65mm) for some Kevlar fishing string I have and quickly decided I would never be making doilies.
Thank you Mike!! I can always count on you to answer my questions! 
I honestly didn’t think that was the answer you were looking for.
I thought you were thinking more like the smallest aluminum (B-2.25mm).
This page has a hook size to thread size comparison.
So you could buy the hooks for the size thread you can find or the size thread for the hooks you can find.
I have Crochet with very fine hooks in the past, but I am sure it will now be very hard to find the fine yarn, to complete a project.
[color=#300090]
Crochet thread (often cotton) comes in US sizes (given in order from larger to smaller) #3, #5, #8, #10, #20, #30, #40 and smaller.[1] Size 20 is the smallest I have used. I find it nearly as small as sewing thread.
Over at [B][U]Yarn Standards[/U][/B], the smallest “steel” hook size is given as #14 US or 0.9mm.
About dot com gives a [U][B]Hook Size To Use With Thread Size[/B][/U] chart that you may find helpful.
In the past I could find crochet cotton thread in size #3, #5, #10, and #20 in Walmart. Now the selection is reduced and colors were always limited.
[/color]