To convert the fraction $\frac{2}{3}$ into a decimal:

1. Divide 2 by 3.
2. $2 \div 3 = 0.6666\ldots$, which is a repeating decimal. It can be written as $0.\overline{6}$, where the bar over the 6 indicates that the 6 repeats indefinitely.

So, the correct answer is the option $0.\overline{6}$.

Do you have any questions, or would you like further details?

Here are some related questions:

1. How would you convert $\frac{5}{6}$ into a decimal?
2. What is $0.\overline{3}$ as a fraction? 3