C <- matrix(1:3)
W <- matrix(2:4)
S <- matrix(3:5)

> K
      [,1] [,2] [,3]
[1,]    C    0   0
[2,]    0    W   S

> C <- matrix(0, 3,2)
> W <- matrix(1, 4,5)
> S <- matrix(2, 6,7)
> bigM <- matrix( list(), 2, 3)
> bigM[1,1] <- list(C)
> bigM[2,2] <- list(W)
> bigM[2,3] <- list(S)
> bigM
     [,1]      [,2]       [,3]
[1,] Numeric,6 NULL       NULL
[2,] NULL      Numeric,20 Numeric,42
> bigM[2,3][[1]][42]
[1] 2