Nicole Kidman thinks beauty is about being ''strong and healthy''.

The 50-year-old actress - who has daughters Sunday, nine, and Faith, six, with her husband Keith Urban, as well as adopted children Isabella, 24, and Connor, 22, with her ex-husband Tom Cruise - has revealed the lessons she's trying to pass on to her two youngest kids.

Nicole explained she tells her daughters that beauty is about ''being strong and healthy, and feeling good inside so you can feel good outside''.

The Hollywood star also claimed there is an increased onus on mothers to take care of their health, as women are increasingly having children later in their lives.

Nicole told E! News: ''We all know women are having children later in life. So they need to be healthy and strong for their children. It's really important.''

And Nicole said that having ''beautiful, healthy-looking skin'' was the key to feeling good later in life.

She explained: ''You want to have beautiful, healthy-looking skin and that's what I think most women would desire.

''And, as much as we talk about anti-ageing, it's more that I want to feel vibrant.''

Meanwhile, Nicole recently revealed she considers her family to be her biggest passion in life.

The award-winning actress may be known across the world for her talents in front of the camera, but the Australian beauty insisted her first priority is her family.

She said last month: ''My big passion is just my family; my love.

''My daughter said to me, 'You and Daddy kiss all the time.' I thought, 'That's such a fantastic thing for your daughter to say to you.' And that's my passion.

''I know it's a simple answer, but I'm deeply passionate about raising my children and being with my husband.''