By and by
Definition 1 of 2
Pro Tip 1/3Expectation of Delay
Indicates something will occur soon but not immediately, suggesting a short wait. 
She said she'd join us by and by, once she finishes her work.
Pro Tip 2/3Narrative Transition
Used in storytelling to imply a seamless passage of time without detailing every moment. 
By and by, the caterpillar transformed into a butterfly.
Pro Tip 3/3Calm Reassurance
Often used to reassure someone that an event or action will eventually happen. 
Don't worry, your bike will get fixed by and by.