Prostrate, small backyard weed to be identified. I suspect it is in the portulaca family. I paged through the family in the Jepson Manual without recognizing this. I didn't find it in Google Images or the USDA web site. The longest leaf was about 1 cm (3/8 inch), counting petiole. Leaves and bracts look somewhat succulent, often with red tinge at edges, like miners lettuce and red maids. Very small flowers, about 1 mm diameter except for the calyx or involucre (under 2 mm diameter), which hides the rest of the flower most of the time. I finally photographed a flower that was fully open.
Flower after awkwardly cutting away sepals (or involucre) and some petals; held by one sepal/involucre part, I think. See ovary, three anthers, and three-part strigma. The stigma has either a rough surface, or yellow pollen. I vote for yellow pollen; I see the yellow grains on other surfaces, such as the ovary! Stamens inserted alternately to the petals, part way up the inside of the calyx. Much easier to understand the view in the stereo microscope! Unimac lens at 2.6 zoom.
Flower after awkwardly cutting away sepals (or involucre) and some petals; held by one sepal/involucre part, I think. See ovary, three anthers, and three-part strigma. The stigma has either a rough surface, or yellow pollen. I vote for yellow pollen; I see the yellow grains on other surfaces, such as the ovary! Stamens inserted alternately to the petals, part way up the inside of the calyx. Much easier to understand the view in the stereo microscope! Unimac lens at 2.6 zoom.