Nicole Richie thinks her kids are hilarious.

The 'Fashion Star' mentor - who has a five-year-old daughter, Harlow, and son Sparrow, three, with her husband Joel Madden - has revealed she keeps a memory box full of ''adorable things'' that her children say.

The 31-year-old star told ''Kids are so funny. My mom told me you should write down every cute thing that they do because you will forget.

''Joel and I really write down every adorable thing they do and save them.

''When my son falls down, I just think it's so funny. I know it's horrible, but it is so funny and he doesn't have that far to go down anyway. It's so, so bad of me!''

The 'House of Harlow' designer isn't sure whether her children will follow in her stylish footsteps by creating their own fashion line.

She said: ''We'll have to see. I try to stand back and support.''

Nicole, who has just launched a new web series on AOL based on her Twitter feed called 'Candidly Nicole', recently admitted that she is enjoying her freedom more as her children get older and isn't sure whether she would like to have another baby.

She said: ''I'm just chillin'. Let me just chill! I really like that they're doing their own thing. They're at school until 3. I don't have to, like, look after them -- or even think about them! It's like every other day.''

Asked if she would like more children, she said: ''I don't know,'' and insisted she doesn't like to gush about her children too much.

She explained: ''They want to talk about their spit-up and how cute their boogers are. I try to not be that mom. I know what is really cute and what I only think is cute.''