Nesting hearts are a great way to talk about size with your little one. You can use different size cookie cutters or cut out the different sized hearts and talk about which ones are big which ones are small. You can even compare and ask you child to find the bigger heart or the smaller heart.
Toddlers are just beginning to classify objects, meaning they can separate one type object from another but only based on one difference between the two categories (dinosaur toys versus car toys). Their understanding of size and color, though, are still quite limited. It's fun to talk about color and size with little ones, but they may not be ready to permanently know that information. Toddler minds are bursting with so much new information everyday that it takes a very long time to sort out all that information and make sense of it. That's the job of toddlerhood! For that reason, it's good to plant the seeds of what they need to know (everything!) and wait for those seeds to take root and grow. While we're waiting, we keep playing the same games again and again.
Back to the hearts! These fun hearts can also be turned into Valentine's Day decorations. Layer the hearts from biggest to smallest and glue them together. You can further decorate them with ribbon, glitter, cardboard cutouts, anything you have on hand. To give some depth I used foam squares. Then I attached string and/or ribbon to hang them up with. You could also use yarn. I hung them between the kitchen and living room where the ceiling drops down.
Happy Valentine's Day!