In 1907, Apollinaire introduced Picasso to Georges Braque,
another young  painter deeply interested in Cézanne.  Braque and
Picasso worked together  closely; Braque later said they were "roped together
like mountaineers" as they  explored a new approach to organizing
pictorial space.  While "Les Demoiselles"  cleared the ground, Cubism
was a joint construction, to the extent that  sometimes Picasso
and Braque could not tell their work apart.  Afterwards,  describing
Braque's role in Cubism's later evolution, Picasso called him "just
a  wife," simultaneously dismissing both his colleague and women.
 But Braque's  integral role in Cubism's initial invention cannot
be disputed.  
During the summer of 1908 Braque went to L'Estaque, in
southern France, where  his idol Cézanne had painted before him.
 The way in which Cubism sliced and  diced pictorial space, attempting
to see all angles at once, to paint an  analysis of a form instead
of its appearance, is illustrated by the comparison  of Braque's
painting "Houses at L'Estaque" with a photograph of the view that
 Braque was painting.  (The photograph was taken by Picasso's dealer, Daniel-
Henry Kahnweiler.)  Scale and perspective are gone; forms are simplified
 into blocks.  There is no distinction between foreground and background;
the  shapes of the painting seem to be stacked on top of each other.
The influence of Braque and Cézanne is clear in Picasso's
paintings from the  summer of 1909, which he spent with Fernande
in Horta de Ebro.  Braque and  Picasso had extended Cézanne's method
landscape painting to the point where a  view became an almost monochromatic
field of faceted forms.
This method, extended and developed, led to paintings
that were almost  indecipherable combinations of fragmented facets
in grays and browns. Kahnweiler was later to name this stage of
Picasso and Braque's work  Analytical Cubism, because it was based
on an analytical description of  objects.  Picasso's portrait of
Kahnweiler, in which he splits up his sitter  into a multiplicity
of discontinuous surfaces, exemplifies his work during this  period,
showing how far he took the results of his summer in Horta.  Describing
 this period, Kahnweiler wrote, "The great step has been made. 
Picasso has  exploded homogenous form."  Indeed, Cubism was an explosion; not
only did Cubist  paintings resemble the shrapnel of their ostensible
subjects, but the intent was  a kind of joyous destruction of the tradition
of Western painting and the result  was a revolution in art history.
Meanwhile, Picasso had grown tired of his struggling-artist existence
at the  Bateau-Lavoir; in the fall of 1909, he and Fernande moved
to an new apartment,  with a maid, near the Place Pigalle in Paris.
 He exhibited internationally,  from Moscow to New York.  His collaboration
with Braque continued, and the two  spent the August of 1911 together
painting in Céret.  There he began working  with more easily legible
imagery than that used in the nearly abstract work of  the year
before.  Braque began stenciling letters and words on his paintings,
 and Picasso followed suit; his word-filled paintings became riddles,
puns and  love-tokens.  Picasso began a new affair in the fall of
1911, with  Eva  Gouel; instead of painting portraits of her, he
marked the presence of this  new muse by incorporating the words
"ma jolie," meaning "my pretty," into his  paintings.