Use the figure of the first quadrant of the unit circle to find the exact circular function value. \[ \tan 0 \]

Step 1 ：The tangent of an angle in the unit circle is defined as the ratio of the y-coordinate to the x-coordinate of the point where the terminal side of the angle intersects the unit circle.

Step 2 ：For an angle of 0 degrees, this point is (1,0).

Step 3 ：Therefore, the tangent of 0 degrees is 0/1 = 0.

Step 4 ：The exact circular function value of \(\tan 0\) is \(\boxed{0}\).