This is documentation for Mathematica 8, which was
based on an earlier version of the Wolfram Language.
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Rearranging Nested Lists

You will encounter nested lists if you use matrices or generate multidimensional arrays and tables. Mathematica provides many functions for handling such lists.
Flatten[list]flatten out all levels in list
Flatten[list,n]flatten out the top n levels in list
Partition[list,{n1,n2,...}]partition into blocks of size ××...
Transpose[list]interchange the top two levels of lists
RotateLeft[list,{n1,n2,...}]rotate successive levels by places
PadLeft[list,{n1,n2,...}]pad successive levels to be length

A few functions for rearranging nested lists.

This "flattens out" sublists. You can think of it as effectively just removing all inner braces.
In[1]:=
Click for copyable input
Out[1]=
This flattens out only one level of sublists.
In[2]:=
Click for copyable input
Out[2]=
There are many other operations you can perform on nested lists. More operations are discussed in "Manipulating Lists".