in diapers
Meaning
in the very early stages of development
Used other than figuratively or idiomatically: wearing a diaper, or needing to wear diapers.
Source: en.wiktionary.orgExamples
Keeping children in diapers beyond infancy can be controversial, with family psychologist John Rosemond claiming it is a "slap to the intelligence of a human being that one would allow baby to continue soiling and wetting himself past age two."
Detainees were clad only in diapers and not allowed to feed themselves.
I haven no idea what I'm in for because my kid's still in diapers and, from the looks of the increasingly bigger sizes, he might technically never outgrow them.
Let’s just say I had a bucket load of explaining to do to Kay and Ray Howard, my extremely Catholic parents, when I landed on their swank new doorstep with Laura and Vivs both still in diapers.
While her son, Will, was in diapers as a one-year-old, her daughter Eden, who had spent time with a foster family, had been started on elimination training before her first birthday.
In 2007, when the iPhone was introduced, the oldest millennials were freshly out of college, and the youngest of them were still in diapers.