There are over a billion Catholics around the world, and women have always played a significant role in the life of the Church - but have been excluded from the Catholic hierarchy. A number of devotees feel called upon to serve God as priests, but the Vatican has never allowed female ordination to priesthood. Now, there's a growing movement to change this. Over 200 women have chosen to take part in secret ordination services, despite knowing they will be excommunicated from the Church. BBC 100 Women follows two women who have been unofficially ordained in the US and Colombia. Is there a future for women priests? And can this change happen in our lifetime?