The process whose specific outcome is the progression of the epidermis over time, from its formation to the mature structure. The epidermis is the outer epithelial layer of a plant or animal, it may be a single layer that produces an extracellular material (e.g. the cuticle of arthropods) or a complex stratified squamous epithelium, as in the case of many vertebrate species [goid 8544] [pmid 11039935] [evidence NAS]; The process whose specific outcome is the progression of an embryo from its formation until the end of its embryonic life stage. The end of the embryonic stage is organism-specific. For example, for mammals, the process would begin with zygote formation and end with birth. For insects, the process would begin at zygote formation and end with larval hatching. For plant zygotic embryos, this would be from zygote formation to the end of seed dormancy. For plant vegetative embryos, this would be from the initial determination of the cell or group of cells to form an embryo until the point when the embryo becomes independent of the parent plant [goid 9790] [pmid 12270937] [evidence NAS]; The process whereby relatively unspecialized cells, e.g. embryonic or regenerative cells, acquire specialized structural and/or functional features that characterize the cells, tissues, or organs of the mature organism or some other relatively stable phase of the organism's life history. Differentiation includes the processes involved in commitment of a cell to a specific fate [goid 30154] [evidence IEA]; Any process that activates or increases the frequency, rate or extent of signal transduction mediated by the JNK cascade [goid 46330] [pmid 12270937] [evidence IDA]; Any process that activates or increases the frequency, rate or extent of activity of the transcription factor NF-kappaB [goid 51092] [pmid 11039935] [evidence IDA]; Any process that activates or increases the frequency, rate or extent of signal transduction mediated by the JNK cascade [goid 46330] [evidence ISS]; Any process that activates or increases the frequency, rate or extent of activity of the transcription factor NF-kappaB [goid 51092] [evidence ISS]