The doorbell rang repeatedly as Monica walked down the stairs. "I'm coming!" Monica yelled. She was in a bath robe, drying her wet hair with a towel. She flung the door open to see no one on the other side. She looked at the doorbell and saw a piece of tape holding the button down. "Damn kids." She pulled the tape off and was about to go back inside when she noticed a box on the ground. She picked it up and took it inside.

Meanwhile, her 17-year-old son Josh had just woken up. It was the first day of his summer vacation. He put on some pants and a shirt and walked downstairs. "Hey mom," he said, seeing his mother sitting in the living room looking at the mysterious box.

"Hey honey."

"What's that?" he asked.

"I don't know. It was on the porch. It doesn't have any stamps or a return address or anything."

"You gonna open it?"

"Mmkay," Monica said as she leaned forward and pulled the tape off the box. That position gave Josh a pretty good view down her bathrobe and he could see a nice amount of cleavage. As much as he hated to admit it, he had the hots for his mom. She was the most attractive woman Josh knew, even more than any of the girls at his school. At 34 years of age, Monica looked amazing. She had a beautiful face, a great round ass, and amazing D cup breasts. Monica looked up at her son and he quickly looked away. She smirked to herself and opened the box.

"A bra?" Monica said quizzically as she held up a neon green bra. "Why would someone send me a bra? I don't think it's even my size." She pulled out a piece of paper and read aloud, "'Congratulations! You have been chosen at random to try out I.F.S.'s latest product: The Expando-Elastibra! The material in the bra allows it to fit snuggly on any breast size up to J cups.'" Monica stopped reading and looked at the bra. "No way. This little thing?" She tried pulling it with her hands and it stretched to an immense size. "Whoa."

"Huh," Josh said. "Well I'm going to take a shower."

"Alright, I'll see you when I get home from work," Monica said as she studied the stretchy bra, curious as to how it worked.

Josh headed upstairs into the bathroom as Monica took the box and went into her bedroom. She dropped the bra on her bed and looked at it as she contemplated whether or not she should wear it. "Eh, what's the worst that could happen?" She untied her bath robe and pulled it off her bare body. Then she grabbed the bright green bra, stretched it over her breasts, and fastened the clasp behind her. She looked at herself in the mirror. "Hmmm. Feels pretty comfortable," she said to herself, analyzing her new bra, "but I would have picked a different color." She grabbed her work blouse and put it on next.

Josh turned off the shower and grabbed a towel to dry himself. Suddenly, he heard a scream coming from downstairs. He quickly wrapped the towel around his waist and ran downstairs into his mother's room. "Mom? What's wrong? I heard a scream," he said as he opened her door. He walked into her room to see her wearing her work blouse and nothing under her waist. He couldn't help but stare at her beautiful trimmed pussy. The most he had seen of his mother's body was when she wears a bathing suit. He had never seen her bare pussy before. Monica didn't seem concerned at all that she was baring her vagina to her own son. She had other things on her mind.

"Josh! That bra is doing something to my tits!" Monica said, frantically.

"What do you mean? What's it doing to your uh ... tits?"

"Just look at them!"

Josh gladly looked at his mother's chest. He didn't notice anything at first, but then he saw what she meant. Her breasts were growing in size. Josh could feel his dick slowly hardening as he stared at her breasts straining against her blouse. Remembering that he only had a towel covering himself, he tried to think about something else, but his eyes kept going back to his mom's growing bosom.

"Hold on, maybe it says something on this," she said as she grabbed the piece of paper out of the box and started reading it. "'We at Intimate Fantasy Services have engineered a way to temporarily increase breast sizes at a dramatic rate by manipulating the hormones in the mammary glands. The Expando-Elastibra was developed specifically for fans of breast expansion.'"

Monica's blouse was quickly filling up and tightening against her breasts.

"'After putting on the Expando-Elastibra, the wearer will experience three stages. The first is rapid breast growth.'"

The top button shot off Monica's blouse, revealing the faintest hint of cleavage.

"'The second stage is increased sensitivity.'"

Two more buttons flew across the room. Josh was awe struck as he stared at his mother's new cleavage. Monica looked down at her growing breasts and then at Josh, noticing the large bulge pushing against his towel. Monica had never thought of her 17-year-old son in any way other than motherly, but she had to admit that he had a nice package.

A fourth button popped off Monica's blouse and hit Josh in the face. That pulled him out of his daze and he looked up at his mother's face as she looked up into his face. She quickly looked back down at the sheet of paper and continued reading.

"'The third stage is uncontrollable lac-' OH GOD!"

Monica fell back onto her bed and grabbed her breasts.

"Oh my god! It feels so good!" she said as she continued groping herself. "This must be the increased sensitivity. Mmmmm!"

Josh became rock hard watching his own mom wriggling in pleasure. He could make out her stiff nipples through the fabric of the bra. Monica thrust her chest into the air, causing another button to fly off. Her breasts were now bigger than her head. The bra was straining tightly against her chest pillows.

Monica opened her eyes as she felt a sudden discomfort. "GAH! TOO TIGHT!" Monica yelled. "Josh, take it off please!" Josh leaned close to his mom and looked for the clasp. "It's on the back! Hurry!"

"Take your blouse off and turn over," Josh told his mom. She tried fumbling with the rest of the buttons on her blouse, but it was taking too long.

"Just get it off quick!" she said.

Josh tried grabbing one of her breasts with one hand, easing his fingers under the bra cup with his other hand, and pulling it over her breast, but they were just too big. Thinking quickly, he leaned forward and slid his hands under the sides of her blouse, reaching for the back of the bra. He hugged her tightly, her growing breasts pushing against him, as he found the clasp with his fingers. He had never taken a bra off a woman before and was having trouble undoing it. As Monica's breasts grew, Josh could feel himself being lifted upwards. He could barely reach the clasp now. Monica looked into his eyes. "Josh, please!" she begged. Determined, Josh reached as far as he could behind her and finally unclasped the bra.

Monica gave a sigh of relief and started laughing at how absurd the situation was. Josh smiled, then realized he was still on top of his mom and quickly pulled himself off. Monica grabbed the bra and tossed it onto the floor, revealing her long, stiff nipples to her son. "I'm glad that's over," she said.

"Uh mom," Josh said pointing at her massive tits. "They're still growing." Monica opened her eyes and looked at her giant breasts.

"Jesus, they're huge!" Monica said, wrapping her arms around them. "I can't even see my nipples anymore" She moved her hands over the tops of her breasts, trying to find her nipples. "Mmm, that feels good!" she said as she began rubbing and squeezing them. She felt them stiffening as she pulled on them.