Jennifer Aniston hasn't ruled out starting a family.

The former 'Friends' star - who has been married twice, to Brad Pitt and Justin Theroux - isn't putting any pressure on herself to have a child because she knows there is science on hand to work ''miracles''.

In an interview with Elle US magazine, she said: ''Who knows what the future holds in terms of a child and a partnership - how that child comes in ... or doesn't?

''And now with science and miracles, we can do things at different times than we used to be able to.''

The 49-year-old actress - who was married to Brad from 2000 to 2005 - and 'Leftovers' star Justin announced their separation in February, after more than two years of marriage and seven years together.

Though both break-ups were heartbreaking at the time, the American star still considers them to have been ''very successful'' marriages.

She admitted: ''My marriages, they've been very successful, in [my] personal opinion. And when they came to an end, it was a choice that was made because we chose to be happy, and sometimes happiness didn't exist within that arrangement anymore.''

Meanwhile, Jennifer has revealed she's chosen not to be on social media because she's determined to retain an element of privacy in her life.

Asked why she doesn't have profiles on sites such as Instagram and Twitter, the actress said: ''The one thing I have is maintaining this little circle of sanctity that's my own.

''If I'm sitting here posting something about my dogs or I'm Boomeranging my coffee mug in the morning, that's just giving away one more piece of something that is mine.''