Adverb
inch by inch (comparative more inch by inch, superlative most inch by inch)
Gradually or incrementally.
Inch by inch I conquered the inner terrain I was born with. Bit by bit I reclaimed the swamp in which I'd languished. I gave birth to my infinite being, but I had to wrench myself out of me with forceps. Fernando Pessoa
It’s like uncovering an ancient fossil inch by inch. Source: Internet
When I got there, they admitted me to their ICU, and slowly, inch by inch, the infection backed off. Source: Internet