This cluster of tiny globes is part of a “thimble” cactus, in a pot on the patio. This variety is native to central Mexico. The cactus consists of these little round buds, each of which has clusters of interlaced white spines. If left on the open ground, it will spread to form large mats like a ground cover.
In late winter, this little cactus produces satiny, creamy yellow flowers. It likes bright light and warm temperatures, although it will tolerate short duration temperatures down to as low as 20 degrees F.
In the photo, the clusters appear near actual size on the computer screen. To see the globes and spines close up, click on the image. By the way, those little spines are extremely sharp and stiff.