Provide definitions/explanations for the following terms: $Nucleosome$ and $Euchromatin$.

(N/A) $Nucleosome$ is a structural unit of a eukaryotic chromosome,consisting of a length of $DNA$ coiled around a core of histones. The negatively charged $DNA$ is wrapped around the positively charged histone octamer to form this structure.
$Euchromatin$ refers to a region of chromatin that is loosely packed and stains lightly during interphase. It is transcriptionally active,meaning the $DNA$ within these regions is more accessible for gene expression.