To simplify the expression \((7t)^2 \cdot (7t)^3\), we can use the power rule for exponents, which states that when multiplying like bases, we add the exponents.
Here, the base is \((7t)\), and we have:
\[ (7t)^2 \cdot (7t)^3 = (7t)^{2+3} \]
Now, we can add the exponents:
\[ (7t)^{2+3} = (7t)^5 \]
Therefore, the simplified expression in exponential form is:
\[ \boxed{(7t)^5} \]