I don't know what it is about 'stuff' and storage - the more stuff you have, the more storage you need, that makes sense. But the more storage you have, the more stuff you seem to have and, consequently, the more storage you need again!
In the kids bedroom for toys; in the bathroom for wet toys or bathroom bits (very handy, especially in my house when my youngest was small); in the utility room for all the junk that tends to accumulate there but for some reason mustn't be thrown away.
Under worktops in the kitchen for extra pots and pan storage maybe, in the garage for all the things you keep in the garage that usually end up in a pile in the corner somewhere, like small garden toys, tennis balls, footballs etc (one day, the garage will be junk free - then there might even be room to put the cars in there!).
The actual storage boxes are clear, so you can see what's inside, but you can choose from three different coloured lids: aqua, black and/or red <----- particularly handy if you're buying these to keep little Johnny's toys separate from little Rosie's.
Thanks to Arriaga at HUKD