Viviana Velez struggled with taking tests and social interactions.
"Communication, talking to other people. They don't understand me," said Velez.
She was a toddler when her family learned why.
"I have autism when I was three years old," she said.
She is one of the thousands of Americans living with what's known as an invisible disability. She doesn't need a cane or a wheelchair, but her autism affects her daily life. (continues)