Before you start: Single crochet · Magic ring crochet
Fine thread: the same stitches, much smaller
What you need
Fine cotton crochet thread (size 30 to 80) or sewing thread, a steel hook of about 1 mm or smaller, good light and, for many people, a magnifier. Steel hook numbers get larger as the hook gets thinner, and brands differ, so choose by millimeters.
Start small
Make a chain and a few rows of single crochet in size 20 or 30 thread first. Then try a tiny amigurumi ball: the same 6-stitch magic ring and 6 increases a round, finished with a drop of stuffing or none.
Rest your eyes and hands often. A hook with a thicker handle is easier on the fingers.