Cold-rolled and heat-treated steel sheet, made of a steel having a composition comprising, by weight percent: 0.10% ≤ C ≤ 0.25% 3.5% ≤ Mn ≤ 6.0% 0.5% ≤ Si ≤ 2.0% 0.3% ≤ Al ≤ 1.2% with Si+AI ≥ 0.8% 0.10% :≤ Mo ≤ 0.50% S ≤ 0.010% P ≤ 0.020% N ≤ 0.008% and optionally one or more elements selected from amongst Cr, Ti, Nb, V and B, such that: 0.01% ≤ Cr ≤ 1.0% 0.010% ≤ Ti ≤ 0.080% 0.010% ≤ Nb ≤ 0.080% 0.010% ≤ V ≤ 0.30% 0.0005% ≤ B ≤ 0.004%, the remainder of the composition being iron and unavoidable impurities resulting from the smelting, said cold-rolled steel sheet having a microstructure consisting of, in surface fraction: - between 10% and 45% of ferrite, having an average grain size of at most 1.3 μm, the product of the surface fraction of ferrite by the average grain size of the ferrite being of at most 35 μm%, - between 8% and 30% of retained austenite, said retained austenite having an Mn content higher than 1.1*Mn%, Mn% designating the Mn content of the steel, - at most 8% of fresh martensite, - at most 2.5% of cementite and - partitioned martensite, the cold-rolled and heat-treated steel sheet having a yield strength YS comprised between 1000 MPa and 1300 MPa, a tensile strength TS comprised between 1200 MPa and 1600 MPa, a uniform elongation UE of at least 10%, a total elongation TE, measured according to ISO standard ISO 6892-1, of at least 14%, a hole expansion ratio HER, measured according to the ISO standard 16630:2009, of at least 20%, and a sum of the product of the yield strength YS by the uniform elongation UE (YS*UE), the product of the tensile strength TS by the total elongation TE (TS*TE), and the product of the tensile strength TS by the hole expansion ratio HER (TS × HER), YS*UE + TS*TE + TS*HER, of at least 56000 MPa%. 0.10% ≤ C ≤ 0.25% 3.5% ≤ Mn ≤ 6.0% 0.5% ≤ Si ≤ 2.0% 0.3% ≤ Al ≤ 1.2% with Si+AI ≥ 0.8% 0.10% :≤ Mo ≤ 0.50% S ≤ 0.010% P ≤ 0.020% N ≤ 0.008% and optionally one or more elements selected from amongst Cr, Ti, Nb, V and B, such that: 0.01% ≤ Cr ≤ 1.0% 0.010% ≤ Ti ≤ 0.080% 0.010% ≤ Nb ≤ 0.080% 0.010% ≤ V ≤ 0.30% 0.0005% ≤ B ≤ 0.004%, 0.01% ≤ Cr ≤ 1.0% 0.010% ≤ Ti ≤ 0.080% 0.010% ≤ Nb ≤ 0.080% 0.010% ≤ V ≤ 0.30% 0.0005% ≤ B ≤ 0.004%, the remainder of the composition being iron and unavoidable impurities resulting from the smelting, said cold-rolled steel sheet having a microstructure consisting of, in surface fraction: - between 10% and 45% of ferrite, having an average grain size of at most 1.3 μm, the product of the surface fraction of ferrite by the average grain size of the ferrite being of at most 35 μm%, - between 8% and 30% of retained austenite, said retained austenite having an Mn content higher than 1.1*Mn%, Mn% designating the Mn content of the steel, - at most 8% of fresh martensite, - at most 2.5% of cementite and - partitioned martensite, - between 10% and 45% of ferrite, having an average grain size of at most 1.3 μm, the product of the surface fraction of ferrite by the average grain size of the ferrite being of at most 35 μm%, - between 8% and 30% of retained austenite, said retained austenite having an Mn content higher than 1.1*Mn%, Mn% designating the Mn content of the steel, - at most 8% of fresh martensite, - at most 2.5% of cementite and - partitioned martensite, the cold-rolled and heat-treated steel sheet having a yield strength YS comprised between 1000 MPa and 1300 MPa, a tensile strength TS comprised between 1200 MPa and 1600 MPa, a uniform elongation UE of at least 10%, a total elongation TE, measured according to ISO standard ISO 6892-1, of at least 14%, a hole expansion ratio HER, measured according to the ISO standard 16630:2009, of at least 20%, and a sum of the product of the yield strength YS by the uniform elongation UE (YS*UE), the product of the tensile strength TS by the total elongation TE (TS*TE), and the product of the tensile strength TS by the hole expansion ratio HER (TS × HER), YS*UE + TS*TE + TS*HER, of at least 56000 MPa%. <EOS>