This is the 4832nd most frequent Russian word.
изнутри
"Изнутри" means "from the inside."
The word 'изнутри' here denotes the perspective or position from the interior of the box.
Он открыл коробку и посмотрел на её содержимое изнутри.
He opened the box and looked at its contents from the inside.
In this context, 'изнутри' refers figuratively to internal, emotional, or psychological aspects of a person.
Человек должен изменяться изнутри, чтобы стать лучше.
A person must change from within to become better.
Here, 'изнутри' describes the direction of deterioration or action taking place starting from within a physical object.