Combining Arrays (two 2x2 into one 4x4)

Questions
1

Hi,

How can I transform:

a = {{4, 1}, {1, 3}};
b = {{-1, -2}, {1, -2}};

into

c = {{4, 1, -1, -2}, {4, 1, 1, -2}, {1, 3, -1, -2}, {1, 3, 1, -2}};

I.M.

2 
In[7]:= Flatten[Outer[Join, a, b, 1], 1]

Out[7]= {{4, 1, -1, -2}, {4, 1, 1, -2}, {1, 3, -1, -2}, {1, 3, 1, -2}}
3

Great, thank you David!