Which number is the smallest?
$4.38 \times 10^{3}$
$4.38 h 10^{2}$
$4.38 \times 10^{-3}$
$4.38 \times 10^{-2}$
438

Step 1 ：The question is asking for the smallest number among the given options. To find the smallest number, we need to compare all the numbers. The numbers are given in scientific notation and normal decimal notation. In scientific notation, the exponent of 10 determines the position of the decimal point. A positive exponent moves the decimal point to the right, making the number larger, while a negative exponent moves the decimal point to the left, making the number smaller.

Step 2 ：Convert all the numbers to the same format for comparison: \(4.38 \times 10^{3} = 4380.0\), \(4.38 \times 10^{2} = 438.0\), \(4.38 \times 10^{-3} = 0.00438\), \(4.38 \times 10^{-2} = 0.0438\), and 438 remains the same.

Step 3 ：Compare all the numbers: 4380.0, 438.0, 0.00438, 0.0438, 438.

Step 4 ：Find the smallest number among them, which is 0.00438.

Step 5 ：Final Answer: The smallest number among the given options is \(4.38 \times 10^{-3}\) which is equal to \(\boxed{0.00438}\).