Feed-in braids
Cornrows that start small and grow thicker as extension hair is fed in, so they look natural at the root.
Also: stitch braids
Feed-in braids are cornrows that begin with the braider's own hair alone and have small amounts of extension hair added gradually along the row. This keeps the start of each braid small and natural and reduces strain at the hairline. Stitch braids are a related style in which the braider uses a fingernail to make neat, even horizontal steps, like stitches, along each row. Both became very popular in the 2010s.