Furniture construction with elastic or spring modules

A mattress comprising:

• a plurality of individual spring assemblies, each spring assembly including:
• a single spring, and
• a single spring cap, the spring cap having a central opening in a body of the spring cap, a portion of the spring dimensioned to pass through the central opening of the spring cap, each spring cap having:
• at least one first attachment fitting, and
• at least one second attachment fitting,
• wherein each first attachment fitting is engageable into or onto and removable from a second attachment fitting of an adjoining spring cap,
• wherein the plurality of individual spring assemblies are adapted to be attached to each other via the first and second attachment fittings, forming the individual spring assemblies into a spring core;
• wherein each spring assembly is separable into a single spring and a single spring cap, the springs separated from the spring assemblies are adapted to stack within each other to form a spring column, and the spring caps separated from the spring assemblies are adapted to stack onto each other to form a spring cap column, and the spring column is adapted to be arranged inside of the spring cap column;
• and
• a top pad on top of a top end of the spring core.