An Instant
Instant, Moment
noun
A blink interval of time is a very short period of time. It's an instant or a moment.
This is a jukugo word that uses the on'yomi readings of the kanji. You should be able to read this on your own.
蜘蛛の巣にぶつかった瞬間に、人は突然空手の達人へと変身する。
The moment they walk into a spider web, people suddenly turn into karate experts.
その瞬間、彼女の目に小さな光が灯った。
In that moment, a small light appeared in her eyes.
時計が時刻を告げた瞬間、全ての通信網が途絶えました。
The moment the clock announced the time, all the communications networks stopped.