Question: When was Picasso's Blue period?
About the article "Pablo Picasso", section "Blue Period".

Candidate passages:
Picasso's African Period, which lasted from 1906 to 1909, was the period when Pablo Picasso painted in a style which was strongly influenced by African sculpture.
This proto-Cubist period following Picasso's Blue Period and Rose Period has also been called the Negro Period, or Black Period. 
The Rose Period comes from the time when the style of Pablo Picasso's painting used cheerful orange and pink colours in contrast to the cool, somber tones of the previous Blue Period.
The Rose Period lasted from 1904 to 1906.
Picasso was happy in his relationship with Fernande Olivier whom he had met in 1904 and this has been suggested as one of the possible reasons he changed his style of painting.
Harlequins, circus performers and clowns appear frequently in the Rose Period and populated Picasso's paintings at various stages throughout the rest of his long career.
The harlequin, a comedic character usually depicted in checkered patterned clothing, became a personal symbol for Picasso.
The Rose Period has been considered French influenced, while the Blue Period more Spanish influenced, although both styles emerged while Picasso was living in Paris.
Picasso's Blue Period began in late 1901, following the death of his friend Carlos Casagemas and the onset of a bout of major depression.
It lasted until 1904, when Picasso's psychological condition improved.
The Rose Period is named after Picasso's heavy use of pink tones in his works from this period, from the French word for pink, which is "rose".
Picasso's highest selling painting, "Garçon à la pipe (Boy with a pipe)" was painted during the Rose Period.
Other significant Rose Period works include: "Woman in a Chemise (Madeleine)" (1904–05), "The Actor" (1904–1905), "Lady with a Fan" (1905), "Two Youths" (1905), "Harlequin Family" (1905), "Harlequin's Family With an Ape" (1905), "La famille de saltimbanques" (1905), "Boy with a Dog" (1905), "Nude Boy" (1906), "Boy Leading a Horse" (1906), and "The Girl with a Goat" (1906).
The Rose Period was followed by Picasso's African influenced period, where his Proto-Cubist work took form.
The most famous painting from Picasso's African Period is Les Demoiselles d'Avignon, painted in 1907, which created a sensation among critics and the public when it was exhibited in 1916. 
The Blue Period () is a term used to define the works produced by Spanish painter Pablo Picasso between 1901 and 1904 when he painted essentially monochromatic paintings in shades of blue and blue-green, only occasionally warmed by other colors.
These somber works, inspired by Spain and painted in Barcelona and Paris, are now some of his most popular works, although he had difficulty selling them at the time.
This period's starting point is uncertain; it may have begun in Spain in the spring of 1901 or in Paris in the second half of the year.
In choosing austere color and sometimes doleful subject matter—prostitutes, beggars and drunks are frequent subjects—Picasso was influenced by a journey through Spain and by the suicide of his friend; Carlos Casagemas took his life at the L’Hippodrome Café in Paris, France by shooting himself in the right temple on February 17, 1901.
Although Picasso himself later recalled, "I started painting in blue when I learned of Casagemas's death", art historian Hélène Seckel has written: "While we might be right to retain this psychologizing justification, we ought not lose sight of the chronology of events: Picasso was not there when Casagemas committed suicide in Paris ...
When Picasso returned to Paris in May, he stayed in the studio of his departed friend, where he worked for several more weeks to prepare his exhibition for Vollard".
The works Picasso painted for his show at Ambroise Vollard's gallery that summer were generally characterized by a "dazzling palette and exuberant subject matter".
Picasso's psychological state worsened as 1901 continued.
In the latter part of 1901, Picasso sank into a severe depressionand blue tones began to dominate his paintings.
Picasso's painting "La mort de Casagemas", completed early in the year following his friend's suicide, was done in hot, bright hues.
The painting considered the first of his Blue Period, "Casagemas in His Coffin", was completed later in 1901 when Picasso was sinking into a major depression.
Picasso, normally an outgoing socializer, withdrew from his friends.
Picasso's bout of depression was to last several years.
Picasso's career had been promising before 1901 and early in that year he was making "a splash" in Paris.
However, as he moved towards subject matter such as society's poor and outcast, and accented this with a cool, anguished mood with blue hues, the critics and the public turned away from his works.
Members of the public were uninterested in displaying the Blue Period works in their homes.
Picasso continued his output, but his financial situation suffered:From 1901 to 1903, he painted several posthumous portraits of Casagemas, culminating in the gloomy allegorical painting "La Vie", painted in 1903 and now in the Cleveland Museum of Art.
The same mood pervades the well-known etching "The Frugal Repast" (1904) which depicts a blind man and a sighted woman, both emaciated, seated at a nearly bare table.
Blindness is a recurrent theme in Picasso's works of this period, also represented in "The Blindman's Meal" (1903, the Metropolitan Museum of Art) and in the portrait of "Celestina" (1903).
Other frequent subjects include female nudes and mothers with children.
Solitary figures dominate his Blue Period works.
Themes of loneliness, poverty and despair pervade the works as well.
Possibly his most well known work from this period is "The Old Guitarist."
Other major works include "Portrait of Soler" (1903) and "Las dos hermanas" (1904).
Picasso's Blue Period was followed by his Rose Period.
Picasso's bout with depression gradually ended, and as his psychological state improved, he moved towards more joyful, vibrant works, and emphasized the use of pinks ("rose" in French) and other warm hues to express the shift in mood and subject matter.
The painting "Portrait of Suzanne Bloch" (1904), one of the final works from this period, was stolen from the São Paulo Museum of Art (MASP) on December 20, 2007, but retrieved on January 8, 2008. 
Les Noces de Pierrette (English:"The marriage of Pierrette") is a painting by the Spanish artist and sculptor, Pablo Picasso.
Painted in 1905, during Picasso's Blue Period; a time when the artist faced poverty and depression following the suicide of his friend Carlos Casagemas in 1901. 
Although "Les Demoiselles" had an enormous and profound influence on modern art, its impact was not immediate, and the painting stayed in Picasso's studio for many years.
At first, only Picasso's intimate circle of artists, dealers, collectors and friends were aware of the work.
While many were shocked and some outraged, influential people such as Georges Braque and Daniel-Henry Kahnweiler were supportive.
Soon after the late summer of 1907, Picasso and his long-time lover Fernande Olivier (1881–1966) had a parting of the ways.
The re-painting of the two heads on the far right of "Les Demoiselles" fueled speculation that it was an indication of the split between Picasso and Olivier.
Although they later reunited for a period, the relationship ended in 1912.
"Les Demoiselles" would not be exhibited until 1916, and not widely recognized as a revolutionary achievement until the early 1920s, when André Breton (1896–1966) published the work.
Richardson goes on to say that Henri Matisse was fighting mad upon seeing the "Demoiselles" at Picasso's studio.
He let it be known that he regarded the painting as an attempt to ridicule the modern movement; he was outraged to find his sensational "Blue Nude," not to speak of "Bonheur de vivre," overtaken by Picasso's "hideous" whores.
He vowed to get even and make Picasso beg for mercy.
Just as the "Bonheur de vivre" had fueled Picasso's competitiveness, "Les Demoiselles" now fueled Matisse's.
Among Picasso's closed circle of friends and colleagues there was a mixture of opinions about "Les Demoiselles".
Georges Braque and André Derain were both initially troubled by it although they were supportive of Picasso.
According to William Rubin, two of Picasso's friends, the art critic André Salmon and the painter Ardengo Soffici (1879–1964), were enthusiastic about it while Guillaume Apollinaire (1880–1918) wasn't.
Both the art dealer-collector Wilhelm Uhde (1874–1947), and art dealer Daniel-Henry Kahnweiler were more enthusiastic about the painting however.
According to Kahnweiler "Les Demoiselles" was the beginning of Cubism.
He writes:Early in 1907 Picasso began a strange large painting depicting women, fruit and drapery, which he left unfinished.
It cannot be called other than unfinished, even though it represents a long period of work.
Begun in the spirit of the works of 1906, it contains in one section the endeavors of 1907 and thus never constitutes a unified whole.<br>The nudes, with large, quiet eyes, stand rigid, like mannequins.
Their stiff, round bodies are flesh-colored, black and white.
That is the style of 1906.<br>In the foreground, however, alien to the style of the rest of the painting, appear a crouching figure and a bowl of fruit.
These forms are drawn angularly, not roundly modeled in chiaroscuro.
The colors are luscious blue, strident yellow, next to pure black and white.
This is the beginning of Cubism, the first upsurge, a desperate titanic clash with all of the problems at once.
(Kahweiler, 1920)