The structure where pollen grains land and stick is called the stigma.

Here's a bit more about it:

* Stigma: The stigma is the sticky, receptive part of the pistil in a flower. It is located at the top of the style, which connects the stigma to the ovary.

* Pollen: Pollen grains are tiny, male reproductive cells produced by the anthers of a flower.

* Pollination: When pollen grains land on the stigma, they germinate and send a pollen tube down the style to reach the ovary, where fertilization can occur.

Let me know if you'd like more details about pollination or any other part of plant reproduction!