Dress in The French Revolution and Empire Periods
This time frame from 1789-1825 is actually several different sub-periods. The first, 1789-1799, the period of The French Revolution, is a sharp transition period. The second 1800-1815 is the time of the French Consulate and Empire, and is a stable Neo-classical period. 1815-1825 is the late Neo-classical period that shows a gradual shift towards the Romantic style.
Dress in The French Revolution
Dress during this period goes through a massive shift. Late 18th Century women's dress collapses from it's padded and puffed look
to a thin, often translucent silhouette. As the French Revolution progressed, different women's styles were adopted that appeared to have reference to the revolutionary politics, social structure and philosophy of the time. In the early 1790's, for example, the "English" or man-tailored style was favored as it hinted towards the leanings of constitutional monarchy. There was a brief fashion for plain dresses in dark colors during the Terror of 1792, but when the Directory took over French fashion again went wild, trying out "Rousseauesque" fashions in "Greek", "Roman", "Sauvage" and "Otaheti" (Tahitian) styles. 
Dress a'la Greque (Hoey) The Psudo-"Greek" look proved most popular and was adopted as the standard style in Europe in the late 1790's
While Men's Costume in the 1790's also becomes thinner in line, it separates it's style from women's dress by beginning to lose nearly all forms of surface decoration, lace and bright color, as "irrational" and feminine effluvia. This change is slow, but it completely alters men's dress by the mid 19th Century into dull dark uniform dress. Other major changes include the adoption of trousers from the dress of sailors and the urban proletariat of the French Revolution, the passing of the fashions for wigs and hair powder, and the (very temporary) demise of the corset.
The bonnet is invented as a hat that is meant to look like a Greek helmet, but it quickly is altered in style out of all resemblance to the original.
Bonnets from "Wiener Zeitschrift", Vienna, 1820 in Max von Boehn's Modes and Manners of the 19th Century The Neoclassical Period 1800-1825
Probably due to post Revolutionary backlash against female influence in politics, later reinforced by the German Philosopher Schopenhauer (who promoted the view that men were supposed to be rational and women emotional), the sexual dichotomy in dress becomes more pronounced in this era, a trend which continues through the 19th Century. The direction of fashions towards Neo Classic dress for women, and increasingly drab utilitarian dress on men, continue in a steady manner in this very stylistically stable period.
1807 
1809 Women's dress locks into a pattern of light colored muslin gowns, high waisted with little puffed sleeves, and psudo-Greek hairstyles, which achieved an apex at the coronation of the Emperor Napoléon in 1804.
Napoleon's sisters at his coronation. As the period proceeds, the originally simple lines of these gowns are increasingly decorated with ruffles and puffs, the skirts get puffed out with petticoats, the waist lowers and tightens with corsets, until by 1825 it is hard to see how the style worn was ever imagined to look Greek.
1822 Vienna from Max von Boehn's Das Beiwerk der Mode, 1928 
Men's dress also keeps on a fairly steady course towards increasing dullness. Fashion magazines continue to push men's dress towards foppish extremes, but men who actually count in the fashionable world tend to push for plainer styles. Beau Brummell, the leader of male sartorial fashion in England in this period was noted for wearing only black with a white shirt for formal evening wear, a marked departure from the style of the previous century. Tubular and fitted trousers also move from a radical fashion statement to everyday wear for most men of the upper classes.
