Nooks, Corners
noun
Corner corners are still corners. Sometimes they're the corners TO corners, so they're the little nooks and crannies that are hard to get at.
すみずみ
This word uses the kun'yomi readings of the kanji you learned, twice, with the second one rendaku'd. You should be able to read this on your own.
今日は部屋を隅々まで掃除しました。
Today I cleaned every nook and cranny of my room.