Solve for $x$. \[ \log x=-3 \]

Step 1 ：The logarithm equation can be rewritten in exponential form. In this case, the base of the logarithm is 10 (since it's not specified), so the equation \( \log x = -3 \) can be rewritten as \( 10^{-3} = x \).

Step 2 ：Now we can calculate \( 10^{-3} \) to find the value of \( x \).

Step 3 ：\( x = 0.001 \)

Step 4 ：Final Answer: \( x = \boxed{0.001} \)