Here is the flower of Fendler's buckbrush (Ceanothus fendleri) at 40x magnification. Its diameter is about 2 mm. Right click for full resolution. The plant flowers usually from June to July. The flower has five petals shaped like scoops along with five stamens in between. The plant is found in ponderosa pine forests of Colorado, and extends south to northern Mexico and north to eastern Wyoming and western South Dakota.
Equipment used: AmScope M150C microscope with Raspberry Pi camera module V2 (8MP).