Introduction:
The smallest three-digit number is the number with the smallest value that contains three digits. In the decimal number system, the smallest digit is 0 and the largest digit is 9. Therefore, the smallest three-digit number is the number that starts with 1 and ends with 0, such as 100.

Explanation:
To find the smallest three-digit number, we need to consider the place value of each digit. In a three-digit number, the place values are hundreds, tens, and units.

Hundreds place:
The smallest digit that can occupy the hundreds place is 1. This means that the hundreds digit can be either 1, 2, 3, 4, 5, 6, 7, 8, or 9.

Tens place:
The tens place can be filled with any digit from 0 to 9. There are no restrictions on the digits that can be placed in this position.

Units place:
Similar to the tens place, the units place can also be filled with any digit from 0 to 9.

Combining the digits:
To form the smallest three-digit number, we need to choose the smallest possible digit for each place value. Therefore, we choose 1 for the hundreds place, 0 for the tens place, and 0 for the units place.

Smallest three-digit number:
By combining these digits, we get the smallest three-digit number, which is 100.

Summary:
The smallest three-digit number is 100, where the hundreds place is occupied by 1, the tens place is occupied by 0, and the units place is also occupied by 0.

The smallest three digit number is 100.