When making bread, how can you tell how developed your dough is? Many professionals can judge just by looking at the dough, but others will grab a piece and make a gluten window with it.
To do this, take a small fistful of dough and stretch it out between your fingers. If the dough rips into think strands, it is barely developed. If it forms into a lumpy sheet that rips easily, the dough is moderately developed. If it forms a smooth, even, translucent sheet without ripping, the dough is highly developed.
All doughs can and should be highly developed before baking. But a highly developed dough is not created just in the mixing and kneeding, for the longer a dough is mixed, the more oxygen is incorporated, which bleaches the flour's color and destroys the wheat's flavor. Many bakers will mix a dough just to moderate development, then give the dough a full fermentation and serveral turns to complete the development before baking.