Marianna Donati, who became the Foundress of the Congregation of the Daughters of the Poor of St Joseph Calasanz, known as the Calasanctian Sisters, was born at Marradi, Florence, Italy, on 26 October 1848. At the age of 13 she made her first Holy Communion and felt strongly that she was being called to religious life. When her first attempt at discerning a vocation, in which she passed some time with the "Vallombrosane" Sisters, remained inconclusive, she returned to her family and entrusted herself to the spiritual guidance of a Piarist priest, Fr Celestino Zini, well known for his personal holiness. It was Fr Zini who perceived the spiritual richness within young Marianna and encouraged her to listen to the voice of the Holy Spirit.

At home, when she broached the subject of living a consecrated life within the convent, her father, Francesco, could not bear the thought of being separated from his loving daughter and adamantly forbid it. Marianna resigned herself to living with private vows to God within the confines of her parents' home. When she was 33 years old, Marianna's mother died and this led her father to become even more attached to her and rely on her presence.

At age 40, when she again expressed her will to leave home in order to take up religious life her father said that in order to leave she must take him, her aunt and sister Gemma with her. "I want you to be near me to close my eyes when my last hour strikes", he pleaded with his daughter. Finally, in March of 1889 at the age of 41, with the counsel of Fr Zini, Marianna was joined by four young women who were ready to serve Christ in the very poor in what would later become the Congregation she had long desired to found. The first residence, where she could accommodate her relatives and first four companions, was located in Florence next to the parish Church of St Julian.

Fr Zini, who had become the Archbishop of Siena on 25 March 1889, was hesitant about the combination of family-with-religious life and earnestly sought better accommodations. Divine Providence soon provided another dwelling in a different neighbourhood and the family-community benefited from more spacious premises. The religious spirit and profound union with the Lord of Mother Celestina, as she was now called, expressed itself in her desire to care for the physical and spiritual well-being of the many children who were victims of abandonment or abuse. She opened her first school outside Florence on 28 December 1889. This fledgling religious community sought to provide a Christian education for these poor children and thereby offer them a chance to live a better adult life, not only based on Christian principles but with practical, profession skills as well, according to the teaching of St Joseph Calasanz. But the joyful adventure of establishing a new religious Order, of training young Sisters in the service of the Lord and neighbour, of expressing maternal love in the education of poor children, also came with a heavy cross.

On 5 June 1890, at the age of 19, one of the founding Sisters and the secretary of the newborn Institute, Sr Maura, became sick with consumption and died. Assisting her in her illness and witnessing her slow and steady decline certainly weighed on the heart of her spiritual mother and Foundress. This illness, sorrowful though it was, proved much more bearable than the sorrowful situations of the children that landed on the Sisters' doorstep.

On 22 January 1891, a woman arrived, saying: "My daughter is in bed, completely bruised by the beating her father gave her. Yesterday evening, the poor thing was not able to sell all the matches and he reduced her to that state. She is sick and I cannot take care of her. Please take her in even for a few days. May God reward you!".

On 19 May 1892, Mother Celestina's spiritual director, co-Founder, and guide, Archbishop Zini, died. She would henceforth be the sole director of the newborn Institute. But her virtue and Fr Zini's wise counsel and Rule assisted her in governing the Institute well and in establishing various communities throughout Italy.

Years later, on a September morning in 1899, another sorrowful situation arose in Livorno. A person brought forward three children "orphaned by law", because their father was condemned to 30 years in prison and his little girls were literally left without food, a roof over their head or any support. This was the beginning of the Order's new apostolate to children of prisoners.

Mother Celestina's accomplishments were possible due to a strong spiritual life. She had great devotion to Jesus Crucified and was an ardent apostle of Eucharistic Adoration. Basing her spirituality on that of St Joseph Calasanz she dedicated herself totally to God's little ones and taught the Sisters to be attentive spiritual mothers and expert educators, guided by maternal love in their delicate duty of helping the children entrusted to their care.

She knew how to instil in her Sisters the spirit of holy poverty. Poverty, in fact, was to mark much of her religious life, especially during the period when in 1922, she undertook the establishment of the Institute at Rome, undergoing considerable financial difficulty. She died in Florence on 18 March 1925. Her cause for Beatification was introduced on 12 July 1982; on 6 April 1998 her heroic virtues were proclaimed and she was granted the title of Venerable.

On Sunday, 30 March 2008 she was beatified during a special Mass in Florence by Cardinal José Saraiva Martins, C.M.F., Prefect of Congregation for the Causes of Saints.