Describe the structure of androecium/stamen.

The stamen (plural stamina or stamens) is the pollen-producing reproductive organ of a flower. Collectively the stamens from the androecium.
Stamen in a flower consists of two parts, the long narrow stalk-like filament, and upper broader knob-like bi-lobed anther.
The proximal end of the filament is attached to the thalamus or petal of the flower. The number and length of stamens vary in different species.
A normal dithecous or dithecous anther is made up of two anther lobes, which are connected by a strip of the sterile part called connective.
Young anther, while it is still in flower bud in T.S., reveals the presence of outermost epidermis. The outermost wall layer lying just below the epidermis is called endothecium or fibrous layer because wall (two radial and inner) develop fibrous thickenings on them except at the junctions of two pollen sacs. Below the endothecium, there are 1-3 middle layers of parenchyma cells.
The cells of the innermost wall layer are radially elongated and rich in protoplasmic contents. This layer is called tapetum. The tapetum forms the nutritive tissue nourishing the developing microspores. The tapetal cells provide nourishment to young microspore mother cells either by forming a plasmodium (amoeboid or invasive type) or through diffusion (parietal or secretory type).