Express {16^{ - 2}} as a power of base 2.

To express \( 16^{-2} \) as a power of base 2, follow these steps:

1. **Rewrite 16 as a power of 2**:
We know that \( 16 = 2^4 \). So, we can rewrite \( 16^{-2} \) as:

\[
16^{-2} = (2^4)^{-2}
\]

2. **Apply the power of a power rule**:
The rule for powers of powers states that \( (a^m)^n = a^{m \cdot n} \). Applying this rule to \( (2^4)^{-2} \), we get:

\[
(2^4)^{-2} = 2^{4 \cdot (-2)} = 2^{-8}
\]

Thus, \( 16^{-2} \) expressed as a power of base 2 is \( 2^{-8} \).