Is there a serious difference between the following three sentences:
I put the toys in the box.
I put the toys into the box.
I put the toys inside the box.
Is there a serious difference between the following three sentences:
I put the toys in the box.
I put the toys into the box.
I put the toys inside the box.
No significant difference between them - in this context. It is a matter of choice and personal style. Nevertheless, people prefer the shorter way as usual: "he is putting the toys in the box".
In other contexts may be differences between them. Be aware that normally the word "into" is a preposition for movement or transformation while inside is preposition for location. Also see that and this.