The whole world is probably smitten with this Russian lady, I mean, who wouldn't? I get a great feed back on this set of printable, thank you, and I think the matryoshkas haven't lost its charm. So, I got a lot of question regarding the "nesting" invitation. Here's how it actually look like when folded, ready to be sent.
Imagine the biggest matryoshka and the "patterned" silhouette beside her is a regular greetings card. Fold them the usual way you'd want to fold a card, it's a "mountain" fold. Do another mountain fold with the 2 smaller ladies and tuck both inside your "card".
Write any desirable messages inside, put it in an envelope, voila. Happy inviting/greeting. :)
You may want to cut all through the connecting matryoshkas. I let few inches between them for safety (so that you won't easily disconnect the 4 ladies) but if you like yours to be clean and you are very confident in your cutting skill, please welcome to snip clean between the matryoshkas.
Imagine the biggest matryoshka and the "patterned" silhouette beside her is a regular greetings card. Fold them the usual way you'd want to fold a card, it's a "mountain" fold. Do another mountain fold with the 2 smaller ladies and tuck both inside your "card". 
Write any desirable messages inside, put it in an envelope, voila. Happy inviting/greeting. :)