This is a pollen grain from a Hawaiian hibiscus.
Pollen grains are the male reproductive cells of flowering plants.
The outer covering of pollen grains, called the pollen wall, is often sculpted in different shapes. Often botanists can tell what kind of plant the pollen came from by the shape. There is some other kind of pollen grain in the lower left corner of this image. You can see it is smaller and has a different outer decoration. This material may not be reproduced in any form without express written permission.