Gromov's list of 7 constructions in differential topology At the 2010 Clay Research Conference, Gromov explained that we know of only 7 different methods for constructing smooth manifolds.  Working from memory, and hence not necessarily respecting the order he used:


*

*Algebraic geometry (affine and projective varieties, ...)

*Lie groups (homogeneous spaces, ...)

*General position arguments (Morse theory, Pontryagin-Thom construction, ...)

*Solutions to PDE (Moduli spaces in gauge theory, Floer theory, ...)

*Surgery (Cut and paste techniques, ...)

*Markov processes


I realise that I only gave 6 constructions; this was the number of separate items listed on his slides, and since he failed to discuss this part, I am left to guess that he either listed two different constructions on one line, which I interpreted to be variants of the same construction, or that failed to include one altogether.
Question How does one construct a smooth manifold from Markov processes?
I asked Gromov after the talk for explanation, but due to the rudimentary nature of my Gromovian, I was unable to understand the answer.  The only word I managed to parse is "hyperbolic," though I wouldn't put too much stock in that.
 A: There is an interview with Gromov: http://www.ihes.fr/~gromov/PDF/rtx100300391p.pdf
Q: (...) an you describe your involvement and how your mathematical and geometric insights can be useful for problems in biology?
Gromov: I can explain how I got involved in that. Back in Russia, everybody was excited by ideas of René Thom on applying mathematics to biology. My later motivation started from a mathematical angle, from hyperbolic groups. I realized that hyperbolic Markov partitions were vaguely similar to what happens in the process of cell division. So I looked in the literature and spoke to people, and I learned that there were so-called Lindenmayer systems. (...)
And his paper on the subject: "Cell Division and Hyperbolic Geometry" http://www.ihes.fr/~gromov/PDF/16%5B71%5D.pdf
I was just reading: Visions in Mathematics: GAFA 2000 Special Volume, Part I.
Gromov's article in the collection, titled: "Spaces and Questions"
has a subsection: "Symbolization and Randomization" which you might find interesting, he discusses "random manifolds" at length and even touches on one of the questions in his talk: assembling combinatorial manifolds out of simplices (i.e. how many triangles).
A: Unfortunately I missed the talk, but on the other hand Gromov have just produced a new paper called 
Manifolds : Where do we come from ? What are we ? Where are we going ? 
It can be found on his web page. From the title I guess there could be some intersection with the talk. In particular in section 11 called Crystals, Liposomes and Drosophila
Gromov is speaking about  "Markov quotients". This sounds like a way to produce "spaces" (generalisation of manifolds, I guess).
http://www.ihes.fr/~gromov/PDF/manifolds-Poincare.pdf
A: I suspect (but am far from certain) that Gromov may be referring to the correspondence between symbolic and hyperbolic dynamics. 
The idea is basically that the 0-1 matrix corresponding to the sparsity pattern of a stochastic matrix encodes a subshift of finite type or topological Markov chain. Usually, however, one goes from the hyperbolic dynamics to the Markov description via a Markov partition or section. 
I am not aware of a way to go in the other direction in general, although placing certain conditions on the Markov process would facilitate the construction of a Markov partition (which can then be made as small as one likes), for which covering sets would constitute an atlas.

Update: So I did a little digging and came across a paper by Coornaert and Papadopoulos called "Symbolic coding for the geodesic ﬂow associated to a word hyperbolic group" (Manuscripta Math. 109, 465–492 (2002), DOI 10.1007/s00229-002-0321-9, PDF available here). In it the authors discuss an idea of Gromov whereby a to each "word hyperbolic group" $\Gamma$ a space with a flow defined up to orbit equivalence is given: this flow is called the geodesic flow associated to $\Gamma$. I quote:

In the case where $\Gamma$ is the
  fundamental group of a compact
  Riemannian manifold $M$ of negative
  curvature, then $\Gamma$ is word
  hyperbolic and [the geodesic flow
  associated to $\Gamma$] is, up to
  orbit equivalence, the geodesic ﬂow on
  the tangent bundle of $M$.

Nowhere, however, is it indicated that the space so constructed is generically a manifold. Still, this construction is quite closely associated with the ideas mentioned earlier, as the introduction to this paper points out.
