diff --git a/matrix/count_islands_in_matrix.py b/matrix/count_islands_in_matrix.py
index 64c595e84..8d53bfd7e 100644
--- a/matrix/count_islands_in_matrix.py
+++ b/matrix/count_islands_in_matrix.py
@@ -5,11 +5,36 @@
 
 class Matrix:  # Public class to implement a graph
     def __init__(self, row: int, col: int, graph: list[list[bool]]) -> None:
+        """
+        Initialise matrix with number of rows, columns, and graph
+
+        >>> m = Matrix(4, 3, [[True, False, False, False], [True, False, True, False], [False, False, True, True]])
+        >>> m.ROW
+        4
+        >>> m.COL
+        3
+        >>> m.graph
+        [[True, False, False, False], [True, False, True, False], [False, False, True, True]]
+        """
         self.ROW = row
         self.COL = col
         self.graph = graph
 
     def is_safe(self, i: int, j: int, visited: list[list[bool]]) -> bool:
+        """
+        Checks if the cell (i, j) can be visited
+
+        >>> visited = [[False, False, False], [False, False, False], [False, False, False]]
+        >>> m = Matrix(3, 3, [[True, False, False], [False, False, True], [False, False, True]])
+        >>> m.is_safe(0, 0, visited)
+        True
+        >>> m.is_safe(0, 2, visited)
+        False
+        >>> m.is_safe(-1, 2, visited)
+        False
+        >>> m.is_safe(1, 5, visited)
+        False
+        """
         return (
             0 <= i < self.ROW
             and 0 <= j < self.COL
@@ -18,7 +43,15 @@ class Matrix:  # Public class to implement a graph
         )
 
     def diffs(self, i: int, j: int, visited: list[list[bool]]) -> None:
-        # Checking all 8 elements surrounding nth element
+        """
+        Checking all 8 elements surrounding nth element
+
+        >>> visited = [[False, False, False], [False, False, False], [False, False, False]]
+        >>> m = Matrix(3, 3, [[True, True, False], [False, True, False], [True, False, True]])
+        >>> m.diffs(0, 0, visited)
+        >>> visited
+        [[True, True, False], [False, True, False], [False, False, False]]
+        """
         row_nbr = [-1, -1, -1, 0, 0, 1, 1, 1]  # Coordinate order
         col_nbr = [-1, 0, 1, -1, 1, -1, 0, 1]
         visited[i][j] = True  # Make those cells visited
@@ -26,7 +59,16 @@ class Matrix:  # Public class to implement a graph
             if self.is_safe(i + row_nbr[k], j + col_nbr[k], visited):
                 self.diffs(i + row_nbr[k], j + col_nbr[k], visited)
 
-    def count_islands(self) -> int:  # And finally, count all islands.
+    def count_islands(self) -> int:
+        """
+        Counts the number of islands in the matrix
+
+        >>> m = Matrix(3, 4, [[True, True, False, False], [False, True, False, True], [True, False, False, True]])
+        >>> m.count_islands()
+        3
+        >>> m2 = Matrix(3, 3, [[True, True, False], [True, False, False], [False, False, True]])
+        2
+        """
         visited = [[False for j in range(self.COL)] for i in range(self.ROW)]
         count = 0
         for i in range(self.ROW):