A substantially pure culture of human neuroepithelial lineage cells comprising: (a) Chx 10-positive human retinal progenitor cells, wherein the Chx 10-positive human retinal progenitor cells comprise at least 90% or at least 95% of the cells present in the culture; or Otx 2-positive human forebrain progenitor cells, wherein the Otx 2-positive human forebrain progenitor cells comprise at least 90% or at least 95% of the cells present in the culture; and (b) a suitable medium for maintaining the viability of the human neuroepithelial lineage cells, wherein the human neuroepithelial lineage cells are derived by the method comprising the steps of: (i) culturing two or more detached human neuroepithelial rosettes derived from human embryonic stem cells or human induced pluripotent cells in suspension, optionally in a retinal differentiation medium, until neurospheres of at least two different progenitor cell types form; (ii) observing one or more morphological characteristic of the neurospheres to identify the progenitor cell types of the neurospheres, wherein the neurospheres that appear phase-bright and golden in colour with a ring-like, outer pseudostratified, laminar structure under bright field microscopy are identified as retinal progenitor cells and the neurospheres observed to have a uniform morphology are identified as forebrain progenitor cells; and (iii) mechanically separating the neurospheres by progenitor cell type, whereby a substantially pure culture of retinal progenitor cell neurospheres and a substantially pure culture of forebrain progenitor cell neurospheres are obtained. (a) Chx 10-positive human retinal progenitor cells, wherein the Chx 10-positive human retinal progenitor cells comprise at least 90% or at least 95% of the cells present in the culture; or Otx 2-positive human forebrain progenitor cells, wherein the Otx 2-positive human forebrain progenitor cells comprise at least 90% or at least 95% of the cells present in the culture; and (b) a suitable medium for maintaining the viability of the human neuroepithelial lineage cells, wherein the human neuroepithelial lineage cells are derived by the method comprising the steps of: (i) culturing two or more detached human neuroepithelial rosettes derived from human embryonic stem cells or human induced pluripotent cells in suspension, optionally in a retinal differentiation medium, until neurospheres of at least two different progenitor cell types form; (ii) observing one or more morphological characteristic of the neurospheres to identify the progenitor cell types of the neurospheres, wherein the neurospheres that appear phase-bright and golden in colour with a ring-like, outer pseudostratified, laminar structure under bright field microscopy are identified as retinal progenitor cells and the neurospheres observed to have a uniform morphology are identified as forebrain progenitor cells; and (iii) mechanically separating the neurospheres by progenitor cell type, whereby a substantially pure culture of retinal progenitor cell neurospheres and a substantially pure culture of forebrain progenitor cell neurospheres are obtained. (i) culturing two or more detached human neuroepithelial rosettes derived from human embryonic stem cells or human induced pluripotent cells in suspension, optionally in a retinal differentiation medium, until neurospheres of at least two different progenitor cell types form; (ii) observing one or more morphological characteristic of the neurospheres to identify the progenitor cell types of the neurospheres, wherein the neurospheres that appear phase-bright and golden in colour with a ring-like, outer pseudostratified, laminar structure under bright field microscopy are identified as retinal progenitor cells and the neurospheres observed to have a uniform morphology are identified as forebrain progenitor cells; and (iii) mechanically separating the neurospheres by progenitor cell type, whereby a substantially pure culture of retinal progenitor cell neurospheres and a substantially pure culture of forebrain progenitor cell neurospheres are obtained.