The Grandma is the main antagonist of Cookie Clicker Classic and the 1.0 Update, and the second cheapest building you can purchase with an initial cost of 100 cookies. She produces cookies at a base rate of 1 cookie per second.
Unlike the Cursor and Farm, Grandmas progress with later buildings very well with the grandma type upgrades, most of which double its efficiency but require 15 or more of a superior building to purchase, and sometimes can be quite expensive, up to 7,500,000,000,000 cookies for Rainbow Grandmas. After all upgrades, each grandma has a CpS of 104857.6 cookies per second herself, not counting the bonuses from One mind, Communal brain sweep, and Elder Pact.
Once you have unlocked 7 grandmas, you unlock the Bingo Center/Research Facility, which (as of 1.036) is currently the only upgrade to make a building four times as efficient, although its price of 1,000,000,000,000,000 cookies means it'll be a while until it's worth the cost. This will unlock a new upgrade after 30 minutes (research only starting once the last item researched is purchased), including five multiplier upgrades (Specialized Chocolate Chips for +1% and costing 100,000,000,000 cookies, Designer Cocoa Beans for +2% and costing 200,000,000,000 cookies, Underworld Ovens for +3% and costing 800,000,000,000 cookies, Exotic Nuts for +4% and costing 3,200,000,000,000 cookies, and Arcane Sugar for +5% and costing 12,800,000,000,000 cookies), one upgrade to double Grandma efficiency (Ritual Rolling Pins for 400,000,000,000 cookies), and three upgrades to greatly increase Grandma output but start the Grandmapocalypse (One Mind for 1,600,000,000,000 cookies and Communal Brainsweep for 6,400,000,000,000 cookies, which each give each grandma +0.02 base CpS per grandma, and Elder Pact for 25,600,000,000,000 cookies which gives each grandma +0.05 base CpS per portal. After all the doubling upgrades those figures are a LOT higher than that.)
Each fully upgraded grandma produces cookies according to the following formula:
Grandmas are twice as productive. "This list contains every unholy deed perpetuated by grandmakind. He won't be checking this one twice. Once. Once is enough."
The Bingo Center/Research Facility can also unlock new upgrades for grandma. Although these upgrades can make grandmas more powerful, they would unlock the Grandmapocalypse as well. The following is a list of all upgrades for Grandma, unlocked in the Bingo Center/Research Facility. Once the Bingo Center is purchased, the Ritual Rolling Pins will be unlocked 30 minutes later and when those are purchased the next upgrade will be unlocked 30 minutes later and so on.
Bingo center/research facility
Grandma-operated science lab and leisure club. Grandmas are 4 times as efficient. Regularly unlocks new upgrades."What could possibly keep those grandmothers in check?...
Ritual rolling pins
Grandmas are twice as efficient. "The result of years of scientific research!"
Each Grandma gains +1 base CpS for each 50 grandmas. Note: the grandmothers are growing restless. Do not encourage them. "We are one. We are many."
Each Grandma gains +1 base CpS for each 50 grandmas. Note: proceeding any further in scientific research may have unexpected results. You have been warned. "We fuse. We merge. We grow."
Each Grandma gains +1 base CpS for each 20 portals. Note: this is a bad idea. "squirm crawl slither writhe today we rise"